In Figure, elevator cabs A and B are connected by a short cable and can be pulled

Question:

In Figure, elevator cabs A and B are connected by a short cable and can be pulled upward or lowered by the cable above cab A. Cab A has mass 1700 kg; cab B has mass 1300 kg. A 12.0 kg box of catnip lies on the floor of cab A, the tension in the cable connecting the cabs is 1.91 x 104 N. What is the magnitude of the normal force on the box from the floor?