How to determine number of tests required for a method?

By looking at a method, is there a rule or a way in which we can determine the statement coverage (or the number of tests) that would be required for a method?

int v(int c, int d) {

  if (c>d) {
    return c;
   }

   int x=0;
   for (int i=c;i<=d;++i) {
          if (i%2==0) {
             x+=c;
             }
             x+=c;
           }
           return x;

}