how do we know in the formual given which one is center(T center) and surface (T surface) and T(0) and when do we use it

23.1. The steady state temperature profile for a wire carrying current is described by T(r)=4gR24gr2+2hgR+Tj where R is the radius of the wire, is the thermal conductivity of the wire, g is the heat generated per unit volume, h is the convective coefficient and Tf is ambient temperature. Calculate the temperature and heat flux at the centre and surface of a wire 3mm in diameter, of thermal conductivity 0.25Wmm1K1, generating heat at a rate of 4000kWm1, and losing this heat to ambient air at 10C with a convection heat transfer coefficient of 40WmW2