A rectangular concrete beam has dimensions b=16 in. and h=30 in. The location of the Gr. 60 reinforcing bars, which are placed all in one row in the bottom of the section, is d=27 in. Using a specified compressive strength of concrete of 5,000 psi and the assumptions and simplifications of the ACI 318-14 Code, find the nominal flexural strength Mn for positive bending if the reinforcing bars are: a. Three No. 9 bars b. Four No. 9 bars c. Three No. 8 + two No. 10 bars d. None (i.e., the beam is unreinforced)