What is the ratio between the maximum elastic moment, my, and the maximum plastic moment, mp, for a solid rectangular section made from a ductile, elastoplastic material? what is this ratio referred to?

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