In 3 m of immediate roof of an coal in u/g, bottom 2 m layer of sand stone of fine grained layer, has an RMR of 45, while upper 1 m of coarse grained sand stone has RMR of 30. What will be the over all RMR of the immediate roof?

A. 60

B. 50

C. 30

D. 20

E. 40

Answer: Option E