A scuba diver dove from the surface of the ocean to an elevation of −99 9/10 feet at a rate of −21 feet per minute. After spending 11 minutes at that elevation, the diver ascended to an elevation of −28 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.