This is the start code

I'm confusing how to get started, full answer will be appreciated tho

6 #include 7 #include 8 #include 9 using namespace std; 10 using stringIn = const string&; 11 12 13 extern string ASSIGNMENT; 14 15 void printTitle(); 16 string getInput(); 17 double letterTopoints(stringIn letterGrade); 18 void printReport(double points); 19 20 // Constants 21 const double INVALID_COMBINATION = -1.0; 22 const double INVALID_INPUT = -2.0; 23 24 /** 25 * Calculates the grade points for a letter grade. 26 * @return for success. 27 28 int run() 29 { 30 // Don't change anything inside this function 31 32 printTitle(); 33 string letterGrade = getInput(); 34 double points = letterToPoints(letterGrade); 35 printReport(points); 36 37 return; 38 } 39 40 41 Homework 3 A Grade Calculator grade into a numeric grade point. Here are the details: that translates a letter Letter grades are A, B, C, D, and F, possibly followed by + or - Their numeric values are 4, 3, 2, 1, and 0. In our scheme, there is no F+ or F-, or A+. Adding a + to the grade increases the numeric value by 0.3,a- decreases it by 0.3. If the letter grade is illegal (such as "Z"), then your output should be "INVALID LETTER GRADE"; If the combination is illegal (such as "A+" or "F-") then your output should be "INVALID GRADE COMBINATION"; if there is some other problem with the input, such as too many characters or an invalid symbol (A?), then use "INVALID INPUT". Step 1 - Mock up the Interaction Here is what the program should look like when it runs: sgilbert-H02-Grade Calculator Enter your letter grade: C+ Grade value is [2.3] Go ahead and add the comments to the starter code and use the cout object to pro- duce the output shown in the mockup. As you've done in the previous assignments, remember to separate the input and output values from text that remains unchanged. | Step 2 - Read the Input Ask the user to input a grade, like A or B, along with an optional plus or minus. You can't simply read two characters because the user may not need to enter two, (if there is no plus or minus). STEP 3 PROCESSING THE INPUT PAGE 2 How do you enter a variable number of characters? By using a variable of type string. The string class is defined in the library; you must include this li- brary in any program that manipulates string data. #include using namespace std; Although you might expect >> to read a line of input, the extraction operator actually stops as soon as it hits the first whitespace character, which is any character that ap- pears as blank space on the display screen; this includes spaces, tabs and newlines. The string getline Function To read a line of text, use the string function getline(). getline (cin, name); Create a string variable (I called mine gradeIn) and read the user's input using the getline() function. Here's what your code should look like: // 2. Input section cout 1.7 + Input of D+->1.3 + Input of D->1. + Input of D-->0.7 X Input of Abcdefg: expected (INVALID INPUT) but found (-1.0] X Input of D?: expected [INVALID INPUT] but found [-1.00 ---------------------------------------------- HO3-515: sgilbert:ALL TESTS -- PASS 8/13 (62%). Handling the Postcondition A postcondition is a condition that must always be true just after the execution of some section of code or after an operation in a formal specification. You know that the vari- able gradePoints must be >= 0. if your conversion succeeded. 1. A floating point number if the grade combination istegal (CH) 5. "INVALID LETTER GRADE" if the letter is illegal ("Z") 6. "INVALID GRADE COMBINATION" if the combination is illegal "A+" or "F-") 7. "INVALID INPUT" if there is some other problem with the input Planning an Output Solution Since you have several different error possibilities, use code like this: If grade points is = 0 Print the correct grade point Else If grade input is "A+" or "F+" or "F-" Print invalid grade combination Else If the gradeInput length is >= 1 and the first character is not in the set A,B,C,D,F Print the invalid letter grade message Else Print invalid input 1 http://en.wikipedia.org/wiki/Postcondition 45 + HOMEWORK 3 A GRADE CALCULATOR You can implement the first of these nested conditional statements, easily, like this: // 4. Output section cout = 0) { cout