Please solve in detail for mass transfer

A porous sphere of 1/2 in diameter is saturated with ethanol. The void space of the solid provids sufficient pores su that molecular diffusion Can tate place through the liguid in the passage. The sphere is dropped into alarge, well agitated reservoir of pure water at 10C. If the effective diffusivity of 557cm2/s Cakulate the concentration of ethanat at the center of the sphere ofter soh