Determine the flexural capacity, ÏMn for the singly reinforced rectangular beams having the following properties. Use strength reduction factors from ACI Code. Use beam 1 as a reference, identify the best way to increase the flexural capacity of a reinforced concrete beam and discuss.

Beam No. b (in.) d (in.) Bars f_c (psi) f_y (psi)
1 12 22 3 No. 7 4,000 60,000
2 12 22 2 No. 9 plus 1 No. 8 4,000 60,000
3 12 22 3 No. 7 4,000 80,000
4 12 22 3 No. 7 6,000 60,000
5 12 33 3 No. 7 4,000 60,000