Determine

a$)$ the largest force $P$ that can be applied to the truss if the stress in members $BD,BE,$ and $CE$ is not to exceed $40$ ksi in tension and $30$ksi in compression. All members are of $\frac{3}{4}$ in diameter.

b$)$ The change in diameter of member $BD,E={28}^{**}{10}^3$ksi and $v=0\mathrm{.}27.$