Code:

#include<stdio.h>
int main()
{
float exam_a[20] = { 77, 65, 89, 79, 85, 90, 98, 45, 83, 75, 71, 85, 85, 80, 68, 72, 56, 82, 63, 80} ;
float exam_b[20] = { 87, 92, 84, 89, 75, 99, 92, 66, 80, 77, 56, 79, 76, 78, 88, 78, 66, 70, 69, 90} ;
float exam_c[20] = { 45, 77, 87, 77, 88, 83, 94, 71, 73, 83, 52, 80, 93, 88, 76, 64, 75, 80, 85, 52} ;
int k;
float student[20];
float sum_a = 0, sum_b = 0, sum_c = 0, sum_d = 0, sum_f = 0;
int tot_a = 0, tot_b = 0, tot_c = 0, tot_d = 0, tot_f = 0;
student[k] = exam_a[k] + exam_b[k] + exam_c[k];
student[k] = (student[k])/3;
for (k = 0; k < 20; ++k){
}
if (student[k] >= 95){
printf("%i, 4.0 \n", k);
}
else if (student[k] >= 90){
printf("%i, 3.5 \n", k);
}
else if (student[k] >= 85){
printf("%i, 3.3 \n", k);
}
else if (student[k] >= 80){
printf("%i, 3.0 \n", k);
}
else if (student[k] >= 75){
printf("%i, 2.7 \n", k);
}
else if (student[k] >= 70){
printf("%i, 2.5 \n", k);
}
else if (student[k] >= 65){
printf("%i, 2.3 \n", k);
}
else if (student[k] >= 60){
printf("%i, 2.0 \n", k);
}
else if (student[k] >= 55){
printf("%i, 1.7 \n", k);
}
else if (student[k] >= 50){
printf("%i, 1.5 \n", k);
}
else
printf("%i, 1.0 \n", k);
}}