What is the effective span of staircase, supported at each end by landing spanning parallel with the risers, if the width of landing is 2.5 m, width of starting passage is 1.5 m and going of the stair is 2.2 m?

• A. 6.2 m
• B. 4.2 m
• C. 3.95 m
• D. 4.5 m