lect02c-soln-pizzaArea
pizzaArea with a local variables

  /** pizzaArea
   *  Given a nonnegative diameter diam (in inches), return the surface
   *  area of the pizza top (in square inches).
   *  Accurate to within 1%.
   *    (Test cases omitted to fit on one screen, in lectures.)
   */
  double pizzaArea( double diam ) {
    double radius;
    radius = diam/2;
    return 3.14 * radius * radius;
    }