I believe the answer is 11/15 .
Your answer is 6 because 6 is the smallest number that is divisible by both 2 and 3
Markup=10.82(72/100)≈$7.79 (to nearest cent)
retail=10.82(100+72)/100≈$18.61 (to nearest cent)
I think that would be 100 million pounds of coal.