#include <iostream.h> 
const double pi = 3.14159;
class tank_car {
  public:
    double radius, length;
    tank_car ( ) {radius = 3.5; length = 40.0;}
    tank_car (double r, double l) {radius = r; length = l;}
    void write_radius (double r) {
      cout << "Writing a tank car's radius ..." << endl;  ///
      radius = r;}
    double volume ( ) {return pi * radius * radius * length;}
};
main ( ) {
   tank_car t (3.5, 40.0);
   t.write_radius (4.0);
}