The actual chemistry question was, given that there are 4.19 g of C6H6 how many moles do you have and this is how I solved it and it was wrong.
4.19g/78g/mole = .054 moles of C6H6
I looked up the molar mass of C6H6 and found 78.11.
So 4.19/78.11 = 0.05364 for the digits on my calculator. Are you keying this into a data base of some kind? If so, I suspect the error is because you rounded more than you are allowed. You are allowed 3 significant figures from the 4.19 number so you should have three in the answer. You rounded to 0.054 (just two s.f.) when you should have keyed in 0.0536 (I dropped the last 4 from my answer.). See if that won't take care of the problem. Let me know if this is ok.