How do I even begin to approach this problem????

A realistic model for the climb performance of an Cessna aircraft taking off from an airport at sea level can be given by the relation H(t)=2000ln(t+1), where H represents the aircraft's altitude in feet and t represents its flight time in minutes. At low altitudes, where the air is more dense, the rate of climb is rather good, but as the aircraft climbs higher, the rate decreases.

Find an expression for the rate of climb of the aircraft and estimate its rate of climb 3 minutes after takeoff.

Question

How do I even begin to approach this problem????

A realistic model for the climb performance of an Cessna aircraft taking off from an airport at sea level can be given by the relation H(t)=2000ln(t+1), where H represents the aircraft's altitude in feet and t represents its flight time in minutes. At low altitudes, where the air is more dense, the rate of climb is rather good, but as the aircraft climbs higher, the rate decreases.

Find an expression for the rate of climb of the aircraft and estimate its rate of climb 3 minutes after takeoff.