（2）　　设计一个圆类Circle和一个桌子类Table，在设计一个圆桌类Roundatable，它是从前两个类派生出来的。要求输出圆桌的高度、面积、颜色等数据。其中，类Circle包含数据成员radius和圆面积的成员函数，类Table包含数据成员height和返回高度的成员函数，类Roundtable再添加数据成员color和相应的成员函数。-(2) design a circle class Circle and a table class Table in the the design a roundtable class Roundatable, it is derived from the previous two classes. The required output of the round table data such as height, area, color. Class Circle contains the member functions of the data members of the radius and area of ​ ​ a circle class Table contains data members height and return to the high level of member functions, classes Roundtable add a data member color and corresponding member function.