pointer allocation to 2-d array

#include<iostream.h>
const int kStudents = 25;
const int kProblemSets = 10;

// This function returns the highest grade in the Problem Set array.
int get_high_grade(int *a, int cols, int row, int col)     //1. how is the pointer allocated
 {
 int i, j;
 int highgrade = *a;

 for( i = 0; i < row; i++)
 for( j = 0; j < col; j++)
 if ( *(a + i * cols + j) > highgrade)    //2. How does this line work?
 highgrade = *(a + i*cols + j);
 return highgrade;
}

int main() {
 int grades[kStudents][kProblemSets] = { {75, 70, 85, 72, 84},
 {85, 92, 93, 96, 86}, {95, 90, 83, 76, 97}, {65, 62, 73, 84, 73} };
 int std_num = 4;
 int ps_num = 5;
 int highest;

 highest = get_high_grade( (int *)grades, kProblemSets, std_num, ps_num);
 cout << "The highest problem set score in the class is " << highest << endl;

 return 0;
}