Ahelical compression spring is to be made of oil-tempered wire of 4-mm diameter with a spring index of c = 10. the spring is to operate inside a hole, so buckling is not a problem and the ends can be left plain. the free length of the spring should be 80 mm. a force of 50 n should deflect the spring 15 mm. (a) determine the spring rate. (b) determine the minimum hole diameter for the spring to operate in. (c) determine the total number of coils needed. (d) determine the solid length. (e) determine a static factor of safety based on the yielding of the spring if it is compressed to its solid length.