This one

4. The wave heights h in the open sea is a function of the speed c of the wind and the length of time t that the wind has been blowing at that speed. The table below contains some values of the function h = f (v, t). Here h is measured in feet, 2) in knots, and t in hours. (a) Estimate (with units) f.U and ft at the point (21,15) = (20,15). (b) What is the equation for the tangent plane to the graph of f at the point corresponding to (v, t) = (20, 15)? (c) Describe what f(25, 12) means, and use the tangent plane to ap- proximate it. (d) Estimate (with units) fw, fut, fw and ftt at the point (v,t) (20,15). Waveheight v\\t 5 10 15 20 so 10 2 2 2 2 2 15 4 5 5 5 5 20 5 7 8 8 9 30 9 13 16 17 18 40 14 21 25 28 31