4. The wave heights h in the open sea is a function of the speed 1) 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, 15). Here h is measured in feet, 1) in knots, and t in hours. Wave height 5,1015me 22222 4 5 5 5 5 5 7 8 8 9 913161718 21 25 28 31 (a) Estimate (with units) fv and ft at the point (12,15) = (20, 15). (b) What is the equation for the tangent plane to the graph of f at the point corresponding to (11,15) 2 (20, 15)? (c) Describe what f(25, 12) means, and use the tangent plane to ap proximate it. (d) FIR