Section Modulus calculation and optimization

Calculation for Section 1:

Iox= 2.025e-006m4 =2025000 mm4 (IoxG value from above image)
Y= 430.17 mm
S= I/Y = 2025000 mm4 /430.17 mm = 4707.44 mm3

Yield moment My = S × σy, where σy is the yield strength of the material which is 520 MPa or N/mm2 as mentioned in question.
M= S × σy = 4707.44 mm x 520 N/mm2 = 2447868.8 N mm = 2.4e6 N mm.