If sleeper density is M + 7 for 13 m rails, the minimum depth of ballast under wooden sleepers (25 cm Ã— 13 cm), is

If sleeper density is M + 7 for 13 m rails, the minimum depth of ball

1.	If sleeper density is M + 7 for 13 m rails, the minimum depth of ballast under wooden sleepers (25 cm Ã— 13 cm), is
A.	15 cm
B.	20 cm
C.	25 cm
D.	30 cm
Answer» C. 25 cm