error: ‘imax’ was not declared in this scope

I'm getting the (main.cpp:15:13: error: ‘imax’ was not declared in this scope) error while compiling this code.

Here's the task:

Given k number and kxk z matrix. Get new b[i] vector which elements are taken from the product of the elements preceding the last max element

#include <iostream>
using namespace std;


int indexMax (int z[20][20], int k){
    for (int i = 0; i < k; i++){
        int max = z[i][0];
        int imax = 0;
        for(int j = 0; j < k; j++){
            if (z[i][j]>=max)
            max=z[i][j];
            imax=j;
        }
    }
     return imax;
}
 
int product(int z[20][20], int k){
    int imax=indexMax(z,k);
    int i;
    int P=1;
    for(int j = 0; j < imax-1; j++){
        P*=z[i][j];
    }
    return P;
}
 
int main()
{
    int z[20][20],b[20],k;
    cout << "k=";
    cin >> k;
    
    cout << "Matrix " << k << "x" << k << ":\n";
    for (int i = 0; i < k; i++){
        for (int j = 0; j < k; j++){
            cin >> z[i][j];
        }
    }
    cout << "b[i]:\n";
    for (int i = 0; i < k; i++){
        b[i] = product(z, k);
        cout << b[i] << " ";
    }
return 0;
}