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ISAN-13 is a standard for identifying books. It uses 13 diplts ISBN-13 Formatd. d.d.d.d, ded, Example 9780 1 3 2 sododdad 308 O The last digitd., is a checksum, which is calculated from the other digits using the following formula: 10-(d, + 3d2+ d + 3d. + d + 3d +4, + 3d. + de + 3d. + d + 3dx)%10 of the checksum is 10, replace it with o. 1 Write a function named readstring that takes only an array of character as parameter named data, reads a string of size 13 from the user, and tore it the array data. The function should ask the user to enter a proper string of until the user enters a string of size 13 2. Write a function named checksum that takes only one input parameters str of type char* (null-terminated C strings of characters and calculates and returns the check cum from the first 12 digits 3. Write the main function that Prints your full name and Student ID Define a proper variable to store a e-string Properly call the function readstring to read a 13-digt ISBN Displays valld ISBN it the digit 13 equals the checksum calculated in part2 or invalid otherwise 4. Add your name, your University ID number and section number as a comment at the beginning of this program, Sample Run Name: Abdullah Aret ID:1122333 Please enter a 13 Digit 158N:9780132130806 9780132130806 Valid ISBN