P$15\mathrm{.}18.$ Computer Study $-$ comparison of cantilever andportal methods with an exact analysis. $($a$)$ Deter$-$mine the moments, shear, and axial forces in themembers of the frame in Figure Pl$5\mathrm{.}18,$ using theportal method. $($b$)$ Repeat the analysis using the cantilevermethod. Assume the area of the interior columns is twicethe area of the exterior columns. $($c$)$ Compare the resultswith an exact analysis using a computer software. UseE $=29,000$ kips$/$in for all members; A $=12$ in and I $=600$ in for beams and interior columns; A $=8$ in and I $=400$ in for exterior columns$\mathrm{.}15$ kips$25$ kips$25$ kipsPH$15\text{'}$GB$5$LE$121216$