Water is dripping out from a conical funnel of semi-vertical angle π/4 at the uniform rate of 2 square cms /sec in the surface area, through a tiny hole at the vertex of the bottom. When the slant height of cone is 4 cm, then the rate of decrease of the slant height of water is
A. √24π cm/sec.
B. √2/2π cm/sec.
C. 3√2/4π cm/sec.
D. 1/4√2π cm/sec.