A machine at a post office sends packages out a chute and down a ramp to be loaded into delivery vehicles. $($a$)$ Calculate the acceleration of a box heading down a $10\mathrm{.}010\mathrm{.}0$ slope, assuming the coefficient of friction for a parcel on waxed wood is $0\mathrm{.}100.($b$)$ Find the angle of the slope down which this box could move at a constant velocity. You can neglect air resistance in both parts.