A metal spherical tank is filled with chemicals undergoing an exothermic reaction. The reaction provides a uniform heat flux on the inner surface of the tank. The tank has an inner diameter of 5 m and its wall thickness is 10 mm. The tank wall has a variable thermal conductivity given as k(T) = k₀ (1 + βT), where k₀ = 9.1 W/m∙K, β = 0.0018 K⁻¹, and T is in K. The tank is situated in a surrounding with an ambient temperature of 15°C, the tank’s outer surface experiences convection heat transfer with a coefficient of 80 W/m²∙K. Determine the heat flux on the tank’s inner surface if the inner surface temperature is 120°C.