In an intrinsic semiconductor the energy gap `E_g` is 1.2eV . Its hole mobility is much smaller than electron mobility and independent of temperature. What is the ratio between conductivity at 600K and that at 300K? Assume that the temperature dependence of intrinsic carrier concentration ni is given by `n_i= n_0 exp((E_g)/(2k_BT))` where` n_0` is constant.