1. The problem statement, all variables and given/known data Two boxes each weighing 900 N are stacked on a horizontal floor. Box A is on the bottom, box B is on the top. The coefficient of static friction between box a and the floor is 0.3. A worker applies a force of 600 N to box b parallel to the floor, and the stack moves together along the floor. Which of the following could be the coefficient of static friction between box a and box b? 1) 0.7 2) 0.5 3) 0.4 4) 0.3 5) 0.1 2. Relevant equations Ffriction = mu * Fnormal 3. The attempt at a solution I have no idea how to solve for the coefficient of friction between the two boxes. If it was between the floor and the combination of the two boxes, I would have treated the boxes as one and then find the resulting coefficient of friction. Could anyone please help me get started and solve this problem? Thanks a lot!