$($Rossman $2\mathrm{.}7)$ Your local lumber yard is providing a set of wooden $4$ in $4$ in posts that

you will mount on $6$ in $6$ in concrete bases to support a section of roof. Handbooks

provide the allowable compressive stresses: $1800$ psi $($pounds per square inch$)$ for wood

and $1250$ psi for concrete. The specific weight of concrete $($force per volume$)$ is also

given as $150lb\frac{f}{f}t3,$ although the corresponding number for wood is not shown.

For the post$-$support configuration shown, determine

a$)$ The specific weight of wood, given that a two$-$foot section of the post weighs $21$

lb$.$

b$)$ The allowed load $P$ when the weights of the support and post are included.

c$)$ The allowed load $P$ when the weights of the support and post are not included.