Extracted text: A prestressed concrete beam is perforated with a circular hole as shown in Figure 1. The centroid of a solid beam (before perforated), x is 150mm and y is 460.9mm. According to the condition of the beam, answer the following questions : a. Determine the centroid of the perforated beam. Discuss the differences in the centroid with the presence of holes. b. Calculate the moment of inertias I, and ly of the perforated beam. 150 650 50 r=50 100 Unit in mm 100 100 100 Figure 1