A laminated wood beam on simple supports is built up by gluing together four 2 in. x 4 in. boards (actual dimensions) to form a solid beam 4 in. x 8 in. in cross section, as shown in the figure. The allowable shear stress in the glued joints is 65 psi, and the allowable bending stress in the wood is 1800 psi.
If the beam is 9 ft long, what is the allowable load P acting at the one-third point along the beam as shown? (Include the effects of the beam's own weight, assuming that the wood weighs 35 lb/ft3.)

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3 ft- L=9ft 4 in.