A block of mass M = 439.0 g sits on a horizontal tabletop. The coefficients of static and kinetic friction are 0.671 and 0.441, respectively, at the contact surface between table and block. The block is pushed on with a 12.9 N external force at an angle θ with the horizontal.
a) What angle with respect to the horizontal will lead to the maximum acceleration of the block for a given pushing force?
b) What is the maximum acceleration?