W b Figure 4: Loaded beam An aluminum member of square cross section is loaded as shown in figure 4. For this beam, the maximum normal stress is not to exceed 180 MPa while the maximum shearing stress is not to exceed 80 MPa. The beam is subjected to a distributed load w=2 kN/m and a concentrated load P-1000 N passing by the centroid of the cross section at x-L. For design considerations, L-2m and a=50 mm. a) Identify the critical point of stress in the beam. b) Consider A as the point identified in part a. Determine the minimum allowable value of b for the beam to hold the load shown in figure 4. Round to the multiple of 1 mm. c) If we replace the square cross section by a circular one having the same area, would the beam become safer? Use b-72 mm. You may need some of the following data: