On a skydiving trip, Victor boards a plane which immediately takes off and flies 12 minutes as it
climbs to 8,000 feet. The plane remains at this elevation for 5 minutes and then climbs again
over the next 3 minutes to 10,000 feet. The plane remains at this height for 2 minutes until
Victor makes his jump. He then free falls for 45 seconds until he reaches a height of 3,000
and ueploys his parachute. It takes Victor another 8 minutes to slowly make his way back to the
t was the average rate of change (in feet per minute) of Victor's elevation between
time 12 minutes and 20 minutes?