A tensile-reinforced beam has b = 12 in. and d = 20 in. to the center of the bars, which are placed all in one row. If fy = 60,000 psi and fc' = 5000 psi, find the nominal flexural strength Mn for (a) As = two No. 8 bars, (b) As = two No. 10 bars, and (c) As = three No. 8 bars.