A W 10 x 60 wide-flange beams is subjected to a bending moment M of such magnitude

Question:

A W 10 x 60 wide-flange beams is subjected to a bending moment M of such magnitude that the flanges yield but the web remains linearly elastic.
(a) Calculate the magnitude of the moment M if the yield stress is σY = 36 ksi.
(b) What percent of the moment M is produced by the elastic core?