The diameter of the eye of a stationary hurricane is 20 mi and the maximum wind speed is 100 mi/h at the eye wall, r = 10 mi. Assuming that the wind speed is constant for constant r and decreases uniformly with increasing r to 40 mi/h at r = 110 mi, determine the magnitude of the acceleration of the air at r = 50 mi. (Round the final answer to five decimal places.)