A pipe laid in a drainage layer having cross sectional area of 200 cm2 and length 100 m. The head causing flow is 10 m. It is observed that the pipe got clogged with sand having a coefficient of permeability 10-2 cm/s and subsequently discharge reduced to 2 cm3/s. The length of pipe for which there is clogging is:
1
4 m
2
20 m
3
8 m
4
10 m