5. •• 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 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 0.5 s, how long would this take?