A scuba diver dove from the surface of the ocean to an elevation of −59 9 10 feet at a rate of −11.4 feet per minute. After spending 11.5 minutes at that elevation, the diver ascended to an elevation of −38 9 10 feet. The total time for the dive so far was 18 1 8 minutes. What was the rate of change in the diver's elevation during the ascent? Round your answer to the nearest hundredth. The rate of change of the diver's elevation was ft/min.