The coefficient of static friction between block A and a horizontal floor is 0.320, and the coefficient of static friction between block B and the floor is 0.300. The mass of each block is 2.00kg, and they are connected together by a cord.

If a horizontal force F pulling on block B is slowly increased, in a direction parallel to the connecting cord, until the blocks start sliding, what is the magnitude of F at the instant that they start to slide?