What is the gravitational potential energy stored in a 60 kg boy sitting at the top of a 2 m high slide? (g = 10 N/kg)?

Will you chech and finish these for me, because i am stumped with them.

Determine the maximum r-value of the polar equation r =3+3 cos 0

Consider a 1000 w iron whose base plate is made of 0.5 cm thick aluminum alloy 2024-t6 (ρ = 2770 kg/m3 and cp = 875 j/kg°c). the base plate has a surface area of 0.03 m2. initially, the iron is in thermal equilibrium with the ambient air at 22°c. assuming 90% of the heat generated in the resistance wires is transferred to the plate, determine the minimum time needed for the plate temperature to reach 200°c.