Question

if the combustion of oil yields 4.0x10^4 kj/kg what mass of oil must be burned to yield the number of joules in part b? the answer i got in part b was 7.70 x10^11 J and that it right. for this problem i divided the answer i got 7.70x10^11 by 4.0x10^4 and changed the 4.0x10^4 to joules and then multiplied by 1 kj but i didn't get the right answer.