If a boulder pushed down a hill has 20 Joules of potential energy at the top of the hill, how much kinetic energy does it have once it is at the bottom of the hill?

A12 mm diameter shaft runs in a plain cylindrical bush 30 mm long that is located in an 18 mm diameter hole in a housing. the shaft-inner bush fit is h8 f and the outer bush-housing fit is h7-p6. make a fully cimensioned sketch of the bush with tolerances. find the maximum and minimum clearance or interference for both fits on the inner and outer diameters of the bush