$1.$ Write a function that accepts the name and grade of the student. Grade distribution should be the

following:

A: Score $>=90$

B: Score $>=80$

C: Score $>=70$

D: Score $>=60$

The function should return the following if called

student$\_$grade$($John$,87)$

Output:

The grade of John is B

The program should also print congratulations if the student$$s grade is A

student$\_$grade$($Laura$,90)$

Output:

Congratulations!

The grade of Laura is A

$2.$ Write a function that calculates the square root of a number. The function should employ the ifelse

function. If the value contained in x is negative it should return NA$.$

$3.$ Select any $18$ alphabets from English letters without repetition.