Problem $3(25pts),$ Version B

Block A weighs $400$ lb and block $B$ weighs $600$ lb $.$ If the coefficient of

friction between block A and block $B$ is ${}_A=0\mathrm{.}4$ and the coefficient

of friction between block $B$ and the ground is ${}_B=0\mathrm{.}3,$ determine the

largest horizontal force $P$ that may be applied without causing either

block to move. Let $=30.$ You must prove that neither block moves

for your solution. Draw FBDs$.$