— Do you mind taking the box of books to the office for me?

— ____________ . Put it in my car, please.

A．Yes, I do

B．Not at all

C．Never mind

D．Of course

设平面图形是由曲线

和x+y=4围成的．
(1)求此平面图形的面积S．
(2)求此平面图形绕z轴旋转而成的旋转体的体积V_x．