In the design of beams for a given strength, consider that the conditions of economy of use of the material would avail as follows:
1. Rectangular cross-section is more economical than square section of the same cross-sectional area of the beam.
2. Circular section is more economical than square section.
3. I-section is more economical than a rectangular section of the same depth.
Which of the above are correct?
(a) 1, 2 and 3 (b) 1 and 2 only
(c) 2 and 3 only (d) 1 and 3 only