Rectangular block A weighs $100lb$ and the half$-$circle block B weighs $150lb.$ The surface between block

A and the ground has a coefficient of static friction of ${}_A=0\mathrm{.}2$ and the surface between block A and $B$

has a coefficient of static friction of $B=0\mathrm{.}23.$ If a force was applied at point $C,$ determine the minimum

magnitude of this force to cause impending motion if:

a$)$ The force acts horizontally to the right

b$)$ The force acts horizontally to the left