A box of books weighing 320 N is shoved across the floor of an apartment by a force of 430 N exerted downward at an angle of 35.6° below the horizontal. If the coefficient of kinetic friction between box and floor is 0.57, how long does it take to move the box 3.90 m, starting from rest? I found n to be 260.19 but now i don't know where to go with it. What formula should I use? I can't find one that includes time.