For Problems $5\mathrm{.}5$ to $5\mathrm{.}15,$ determine the design moment strengths $M_n$ of the sections shiown. Use $f_y=60,000$ psi and $f_c^{\text{'}}=4000$ psi, except for Problem $5\mathrm{.}9,$ where $f_c=5000$ psi. Check each section to see if it is ductile.

Problem $5\mathrm{.}15.($Ans$.838\mathrm{.}1ft-k$