A $140-$pound force $P$ is applied parallel to the floor to a $600-$pound block to get it to just begin moving. $($Include a free$-$body diagram as part of your answer for both$)$

a$)$ What is the static coefficient of friction between the block and floor? $(8$ points$)$

b$)$ What is the force required to just move the block if $300$ pounds is added to the top of the block? $(8$ points$)$

This is for applied statics, id appreciate the help and understanding