//<pre>
public class Sphere extends Shape {

   public Sphere(double cx, double cy, double cz, double r) {
      // YOUR CODE GOES HERE
   }

   // RETURNS THE NUMBER OF ROOTS.  ROOTS ARE PLACED IN t[]

   public int traceRay(double v[], double w[], double t[]) {
      // YOUR CODE GOES HERE
      return 0;
   }

   public void computeNormal(double p[], double n[]) {
      // YOUR CODE GOES HERE
   }

   // YOU MIGHT WANT TO DECLARE SOME PERSISTENT VARIABLES
}