C :: Finding Percentages / If Statement / Clear Screen And Reloading Program

For my C programming module, I've been asked to create a program which is basically a ten question mathematics quiz or test if you like. Below is a copy and paste of my current, working program.

Code:

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
int main () {

[Code]....

I am also trying to include into my program; If the user achieves 4 or less marks in the test, they are asked if they would like to repeat the test (have a second chance).

I have been asked by my Lecturer to ask the Question; "Would you like to try again" and the response is 'Y' for yes, 'N' for no. Would this be shown by:

char Y = Y;
char N = N;
printf("Would you like another go?");
scanf(%d%, &Y, &N);

And finally; If the user would like another go, then I am trying to include the code that clears the screen and then reloads the program?

What code is used to clear the screen and no clue what code is written to refresh or reload the program. I assume it's a loop statement or some sort.