A 54 x 54 copper slab of 5cm thick is at a uniform temperature of 299 C. It is suddenly placed in an envioronment maintained at 80 C. Given that slab density is 9101kg/m³, its specific heat is 0.38kJ/k of k, thermal conductivity is 370w/m-k and the convective heat transfer coefficient of environment 90w/m²k. Determine the time at which the slab attains temperature of 96 C. The surface of both sides are taking part in convection.

A 40 x 40 copper slab of 5cm thick is at a uniform temperature of 268 C. It is suddenly placed in an envioronment maintained at 80 C. Given that slab density is 9095kg/m³, its specific heat is 0.38kJ/k of k, thermal conductivity is 370w/m-k and the convective heat transfer coefficient of environment 90w/m²k. Determine the time at which the slab attains temperature of 96 C. The surface of both sides are taking part in convection