What is the daily saving associated with covering windows for 12 hours?

Question

Heat losses from the windows are to be reduced by covering them from inside with a polystyrene insulation(k_ins = 0.027W/mK). Consider application of 25 mm-thick windows (k_w = 1.4 W/m-K). The contact resistance between the glass and the insulation may be approximated as
(R_t,c =0.002 m²K/W), while the convection coefficient at the outside surface of the window is nominally losing heat
(h₀ = 20 W/m²K). With the insulation, the convection coefficient at the inner surface is h_i = 2 W/m²-K; without the insulation it is   h_i = 5 W/m²-K

(i)      What is the percentage reduction in heat loss associated with the use of insulation?

(ii)     If the total surface area of the windows is A_s  = 12 m², what are the heat losses associated with insulated and un insulated windows for interior and exterior temperatures of $T_{\infty },i$ = 20°C and  T $T_{\infty },o$ = – 12°C ?

(iii)       If the home is heated by a gas furnace operating at an efficiency of  $\eta _{f}$= 0.80 and the natural gas is priced at C_g = Rs. 1 per MJ, what is the daily saving associated with covering windows for 12 hours?