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532: Mainline

One step that is easy to take is to convert the display_capacity function, which displays but returns nothing, into capacity, a function that displays nothing but returns a capacity. Recall that display_capacity is defined as follows in the railroad_car class definition:

virtual void display_capacity ( ) { } 

Further recall that display_capacity is defined as follows in the box_car and tank_car class definitions:

virtual void display_capacity ( ) {cout << volume ( );} 

Using those definitions as a model, you might define capacity in the railroad_car class definition as follows:

virtual double capacity ( ) {return 0.0;} 

And you might define capacity this way in the box_car and tank_car class definitions:

virtual double capacity ( ) {return volume ( );}