public static int c(int n, int k) {
// ---------------------------------------------------
// Computes the number of groups of k out of n things.
// Precondition: n and k are nonnegative integers.
// Postcondition: Returns c(n, k).
// ---------------------------------------------------
   if ( (k == 0) || (k == n) ) {
      return 1;
   } 
   else if (k > n) {
      return 0;
   } 
   else {
      return c(n-1, k-1) + c(n-1, k);
   }  // end if
}  // end c