A car is driving northwest at v mph across a sloping plain whose height, in feet above sea level, at a point / miles north and E miles east of a city is given by h(N, E) = 1750 + 150N + 75E. (a) At what rate is the height above sea level changing with respect to distance in the direction the car is driving? rate = (b) Express the rate of change of the height of the car with respect to time in terms of v. rate =