A block of mass M rests on a block of mass M1 = 5.00 kg

which is on a tabletop. A light string passes over
a frictionless peg and connects the blocks. The coefficient of
kinetic friction mk at both surfaces equals 0.330. A force of
46.0 N pulls the upper block to the left and the lower block to
the right. The blocks are moving at a constant speed. Determine
the mass of the upper block.

2 answers

This ones hard....
Help, please!