A solid sphere of radius b=4cm has a cavity of radius a=2cm. The cavity is filled with steam at `100^(@)C`. The solid sphere is placed inside the ice at `0^(@)C`. Thermal conductivity of material of sphere is 0.5 W/m`.^(@)C`. If ther ate of flow of heat through the sphere radially is `x pi J//s` then find the value of x.

Answer

8