make a C program using cramers rule using 3 variables and 3 equations. I need help why the third variable says it isnt initialized and allow the the determinents to be calculated. also i need help making a menu allowing the user to make a start the program and enter the new variables or to exit the program.

This is what i have so far:

#include

#include

int main (void)
{
    int r,c;
    double a[3][3],b[3];
    double x1a, x2a, x3a, x1, x2, x3, d;
    printf("\n Solving for 3 Equations- 3 unknowns\n");

    for (r=0; r<3; r++)
    {
        for (c=0; c<3;c++)
        {
            printf("Enter a [%d][%d]:" ,r,c);
            scanf_s("%lf", &a[r][c]);
        }
d=(a[0][0]*a[1][1]*a[2][2])+(a[0][1]*a[1][2]*a[2][0]) +(a[0][2]*a[1][0]*a[2][1])-(a[0][2]*a[1][1]*a[2][0])-(a[0][0]*a[1][2]*a[2][1])-(a[0][1]*a[1][0]*a[2][2]);

x1a=(b[0]*a[1][1]*a[2][2])+(a[0][1]*a[1][2]*b[2])+(a[0][2]*b[1]*a[2][1])-(a[0][2]*a[1][1]*b[2])-(b[0]*a[1][2]*a[2][1])-(a[0][1]*b[1]*a[2][2]);

x2a=(a[0][0]*b[1]*a[2][2])+(b[0]*a[1][2]*a[2][0]) +(a[0][2]*a[1][0]*b[2])-(a[0][2]*b[1]*a[2][0])-(a[0][0]*a[1][2]*b[2])-(b[0]*a[1][0]*a[2][2]);

x3a=(a[0][0]*a[1][1]*b[2])+(a[0][1]*b[1]*a[2][0])+(b[0]*a[1][0]*a[2][1])-(b[0]*a[1][1]*a[2][0])-(a[0][0]*b[1]*a[2][1])-(a[0][1]*a[1][0]*b[2]);

x1=x1a/d; x2=x2a/d; x3=x3a/d;

printf("\n X1=%lf, X2=%lf, X3=%lf\n",x1,x2,x3);
system("pause");
return 0;
    }}