This is written in C. The program works, but the calculation is wrong, can someone tell me what I am doing wrong?

Thank You

Code:#include "stdafx.h" #include <math.h> #using <mscorlib.dll> using namespace System; // Function prorotypes void sphere_volume (double); // PI is a constant const double PI=3.14159; int _tmain() { // Integer local to Main to store initial radius value double r; printf("Please Enter A Positive Radius Value\n"); scanf("%lf", &r); // If Else Function To Make Sure The User Types A Positive and Not A Negative Integer. if (r >= 0) sphere_volume (r); else printf("You Must Enter A Positive Integer!!!! Not A Negative Integer!!!\n"); return 0; } // This Is The Fnction That Does The Calculations For The Volume. void sphere_volume (double radius) { double radius_cubed; double exponent=3; double volume; printf("This Is The Test To See If R Was Passed To The Function: %lf\n", radius); radius_cubed=pow(radius, exponent); volume=(4/3)*PI*radius_cubed; printf("The Volume Of The Sphere is %lf\n", volume); }