A 80 mm thick steel plate with 400 mm width is rolled to 40 mm thickness in 4 passes with equal reduction in each pass, by using rolls of 800 mm diameter. Assuming the plane-strain deformation, what is the minimum coefficient of friction required for unaided rolling to be possible?

• A. 0.111
• B. 0.158
• C. 0.223
• D. 0.316