$($unit: mm $)$ A process is under statistical control and produces hole parts with a nominal size of $5\mathrm{.}0$ mm $.$ The lower deviation of the hole is $0$ with a tolerance of $0\mathrm{.}015.$ To meet the functional requirements, the allowance of the two mating parts is designed to be $0\mathrm{.}05.$ The tolerance for the shaft is $0\mathrm{.}006.$ The assembly requires that the two mating parts have a clearance fit within $,0\mathrm{.}070].$ Given the process is capable of producing $97\mathrm{.}73\%$ of the holes and shafts that are within specified limits$.$

a$)$ Determine the maximum and minimum limits of hole AND shaft sizes.

b$)$ What is the degree of interchangeability?