A scuba diver dove from the surface of the ocean to an elevation of -69 9/10 feet at a rate of -21.5 feet per minute. After spending 13 minuets at that elevation the diver ascended to an elevation of -8 9/10 feet. The total time for the diver so far was 20 1/8 minutes. What was the rate of change in the divers elevation during the ascent? Round your answer to the nearest hundredth.