SO3 + H2O --> H2SO4, how many grams of SO3 are required to produce 4.00 moles of H2SO4 w/ excess of H2O?

I really cannot understand this question. I multiplied 77.01 times 4.00 divided by 94.03, but I get something else. The answer choices are a) 80.0 g b) 160. g c) 240.g d) 320.g. Could you please explain in very detail how to do this because I utterly forgot. Help! I have like other 5 problems like this so I need to understand the concept. Also, what do they mean by excess of water???