A small box is held in place against a rough wall by someone pushing on it with

Question:

A small box is held in place against a rough wall by someone pushing on it with a force directed upward at 28o above the horizontal. The coefficients of static and kinetic friction between the box and wall are 0.40 and 0.30, respectively. The box slides down unless the applied force has magnitude 13N. What is the mass of the box?