Dynamic 2D Array

#include<iostream>
#include<iomanip>
#include<ctime>
using namespace std;

int ** build2DArray(const int students, const int grades);
void getGrades(int ** gPtr, const int students, const int grades);
void displayGrades(int ** gPtr, const int students, const int grades);
void getAverage(int ** gPtr, const int students, const int grades);

int main()
{
    int students, grades;
    int ** gradePtr;

    cout << "How many students are there? ";
    cin >> students;

    cout << "Enter how many grades there are. (Between 1 and 15) ";
    cin >> grades;

    gradePtr = build2DArray(students, grades);
    getGrades(gradePtr, students, grades);
    displayGrades(gradePtr, students, grades);
    getAverage(gradePtr, students, grades);


    system("pause");
    return 0;
}

int ** build2DArray(const int students, const int grades)
{
    int** ptr;
    if (grades <= 0)
    {
        ptr = NULL;
        return ptr;
    }

    ptr = new int*[students];

    for (int i = 0; i < students; i++)
        ptr[i] = new int[grades];

    return ptr;
}

void getGrades(int ** gPtr, const int students, const int grades)
{
    srand(time(NULL));

    for (int i = 0; i < students; i++)
        for (int*p = gPtr[i]; p < &gPtr[i][grades];)
            *p++ = rand() % 100 + 1;
}

void displayGrades(int ** gPtr, const int students, const int grades)
{
    cout << "STUDENT GRADES" << endl;

    for (int r = 0; r < students; r++)
    {
        cout << "Student " << r + 1 << " Grades: ";

        for (int c = 0; c < grades; c++)
            cout << setw(4) << gPtr[r][c];
        cout << endl;
    }
    cout << endl << endl;
}

void getAverage(int ** gPtr, const int students, const int grades)
{
    float sum = 0.0;
    float average;

    cout << "AVERAGE OF GRADES FOR EACH STUDENT" << endl;
    cout << setprecision(1) << fixed;
    for (int r = 0; r < students; r++)
    {
        cout << "Student " << r + 1 << " Grades: ";
        sum = 0;
        for (int c = 0; c < grades; c++)

            sum += gPtr[r][c];

        average = (sum / grades);
        cout << setw(5) << average;
        cout << endl;
    }
    cout << endl << endl;
}