If the ratio of long and short spans of a two way slab with corners held down is r, the actual reduction of B.M. is given by

• A. (5/6) (r/1 + r²) M
• B. (5/6) (r²/1 + r²) M
• C. (5/6) (r²/1 + r³) M
• D. (5/6) (r²/1 + r⁴) M