A student ate a Thanksgiving dinner that totaled 2800 Cal. He wants to use up all that

Question:

A student ate a Thanksgiving dinner that totaled 2800 Cal. He wants to use up all that energy by lifting a 20-kg mass a distance of 1.0 m. Assume that he lifts the mass with constant velocity and no work is required in lowering the mass.
(a) How many times must he lift the mass?
(b) If he can lift and lower the mass once every 5.0 s, how long does this exercise take?