In a preliminary design for a mail-sorting machine, parcels moving at 2 ft/s slide down a smooth inclined ramp and a horizontal surface with kinetic coefficient of friction μk with the parcel. The spring constant is 180 lb/ft, and the parcel travels 5ft on the horizontal surface before it stops. What is the coefficient of friction μk, if you want the 10-lb parcel to be brought to rest by a linear spring that deflects 5 in. ?