Problem $2.[$Concepts: Internal forces in $2$D and average normal stress$]$ The bars of the truss each have a cross$-$sectional area of $1\mathrm{.}25i{n}^2.$

a$)$ Determine the average normal stress in each member due to the loading $P=8$ kip. State whether the stress is tensile or compressive.

b$)$ If the maximum average normal stress in any bar is not to exceed $20$ ksi $,$ determine the maximum magnitude $P$ of the loads that can be applied to the truss.