A long plate girder is subjected to a maximum bending moment M in which permitted allowable bending stress is fb. The economical depth de and the thickness of the web tw, is given by

• A. <img src="/_files/images/civil-engineering/steel-structure-design/105-14-162-1.png">
• B. <img src="/_files/images/civil-engineering/steel-structure-design/105-14-162-2.png">
• C. <img src="/_files/images/civil-engineering/steel-structure-design/105-14-162-3.png">
• D. <img src="/_files/images/civil-engineering/steel-structure-design/105-14-162-4.png">
• E. none of these.