高数微积分题一道The base of a circular fence with radius 10 m is giv

高数微积分题一道The base of a circular fence with radius 10 m is given by x = 10 cos t; y = 10 sin t.Theheight of the fence varies from 3 m to 5 m such that,at position (x,y),the height is given bythe function h(x,y) = 4 + 0.01(x2 -y2).Suppose that 1 litre of paint covers 100 m2.Sketchthe fence and determine how much paint you will need if you paint both sides of the fence.Ans:5 litre请具体讲一下思路,万分感激!