in c language please

We diagram a pointer variable as a box containing an arrow (a pointer). Here, we diagram three pointer variables. The first points at an integer, the second is uninitialized, and the third contains the NULL pointer. k 31 Integer pointer (points to variable k) Uninitialized integer pointer (points to a random location) NULL pointer (points to location ) Figure 11.2. Pointer diagrams. pl p2 Two uninitialized pointer variables are declared. int *p1, *p2; Base type The asterisk makes a pointer variable Repeat the asterisk for each pointer ? An integer pointer variable is declared and initialized to NULL. int p = NULL; Base type Initializer The asterisk makes a pointer variable 4. Exam grades. Start with the program in Figures 11.12 through 11.14; modify it as follows: (a) In the main program, declare an array to store exam scores for a class of 15 students. Print out appropriate headings and instructions for the user. Call the appropriate functions to read in the exam scores and calculate their mean and standard deviation. Print the mean and standard deviation. Then call the grades() function described here to assign grades to the students' scores and print them. (b) Modify the average () function so that it does not print the individual exam scores during its processing (c) Write a new function, named grades (), with three parameters: the array of student scores, the mean, and the standard deviation. This function will go through the array of exam scores again and assign a letter grade to each student according to the following criteria. Using one line of output per student, print the array subscript, the score, and the grade in columns. The grading criteria are i. A, if the score is greater than or equal to the mean plus the standard deviation. ii. B, if the score is between the mean and the mean plus the standard deviation. iii. C, if the score is between the mean and the mean minus the standard deviation. iv. D, if the score is between the mean minus the standard deviation and the mean minus twice the standard deviation. v. F, if the score is less than the mean minus twice the standard deviation. If a score is exactly equal to one of these boundary limits, give the student the higher grade