public class RationalNumber() i private int num; private int den ; // den != 0 /**Constructs a RationalNumber object. *@param n the numerator *@param d the denominator * Precondition: d !- 0 public RationalNumber (int n, int d) I num = n; /**Multiplies this RationalNumber by r. *@param r a RationalNumber object *Precondition: this.den()!- 0 public void multiply (RationalNumber r) /*missing code */ /*Greturn the numerator public int getNum) /*implementation not shown */ /*@return the denominator public int getDen)t /*implementation not shown */ // Other methods not shown