A $9\mathrm{.}0\mathrm{????}\mathrm{????}$ box of oranges slides from rest down a frictionless incline from a height of $5\mathrm{.}2\mathrm{????}.$ A constant frictional force, caused by friction with the surface from point $\mathrm{????}$ to point $\mathrm{????},$ brings the block to rest at point B$,19\mathrm{????}$ from point $\mathrm{????}.$ What is the coefficient of kinetic friction between A and $\mathrm{????}?$