A soda lime glass sphere of diameter D₁ = 25 mm is encased in a bake lite spherical shell of thickness L = 10 mm. The composite sphere is initially at a uniform temperature, T_i = 40°C, and is exposed to a fluid at T_∞ = 10°C with h = 30 W/m² · K. Determine the center temperature of the glass at t = 200 s. Neglect the thermal contact resistance at the interface between the two materials.