Saved Required information Each of the three rolled-steel beams shown (numbered 1, 2, and 3) is to carry a 64-kip load uniformly distributed over the beam. Each of these beams has a 12-ft span and is to be supported by the two 24-ft rolled-steel girders AC and BD. The allowable normal stress for the steel used is 21.5 ksi. Determine the section modulus for each beam and select the most economical S shape for the three beams using the table given below. (Round the final answer to one decimal place.) Shape S(in') 515 x 429 59.4 S12 x 50 50.6 The section modulus is | The most economical S shape is (Click to select) Help Save