Given the following class interface

class IntPair{ private: int num1; int num2; public: //Question. What's the function prototype to overload the - (subtraction) operator as a // member function, which restricts this operator from modifying either of the // operands? This function will return an IntPair object. 

 // If needed, please use lhs or rhs to refer to the left-hand side // or right-hand side operand in your prototype. Also, if you need to pass in // one or more parameters to this function, you are required to pass it by reference. };