A Standard polystyrene foam is used as thermal insulation for a small refrigerator. The foam has a thermal conductivity of 2-0.035 W/ m C. It is suggested that the same thermal performance can be had with thinner walls (increasing the useful volume) by using a polymethacrylimide foam instead, which has a thermal conductivity = 0.028 W/mC. By what factor can the wall thickness be reduced by this substitution while still maintaining the same thermal performance as before? (6 points)