Outage Notification

I believe that the answer to question 7, part c is wrong.  The answer to question 7, part B should also include the alternative option where friction is also equal to tension.  f = (Mass of block C) x g.

The problem with question 7, part c is that the solutions state that (static friction between A and B) EQUALS (static coefficient between B and A) x (Weight of block B).  That is the same error that many students make.  it is (LESS THAN OR EQUAL TO).  Instead, (static friction between A and B) EQUALS (mass of B) x (acceleration).  That changes the final calculation to:
𝑎=[𝑀_𝐶 − 𝜇_𝑘𝐴 (𝑀_𝐴+𝑀_𝐵 )]𝑔/(M_A+M_B+M_C )

Michael, Thank you so much for your correction. We have updated the problem set on the website. John