in the problem 6b, i found a different answer from your tutor. so which one is actuall the right one?

in the problem 6b, i found a different answer from your tutor. so which one is actuall the right one? power needed=(power needed by long light+bulb )*10*30*3600

this is what i found

 =(100+60)*10*30*3600=172.8*10^6 W or 172.8MW

one feet^3 of natural gas has 1055.1 kJ

so natural gas needed= 172.8*10^6/1055.1*10^3