The simply supported wood beam, fabricated by gluing together four wooden boards, carries the three concentrated forces. The working bending and shear stresses for the wood are 1000 psi and 600 psi, respectively. Determine the largest allowable value of the force P.

 

0.5 in. +|-8 in.|| 0.5 in. 2 in. 2 ft-4 ft- 6 in. 12 in.