SO₂ Reacts with O₂ to Produce SO₃

SO₂ reacts with O₂ to produce SO₃. If 86.0 g of SO₂ is placed in a reaction vessel along with excess oxygen gas, how many moles of SO₂ remain when 50.0 g of SO₃ have been formed?

A) 0.56 mol
B) 0.62 mol
C) 0.72 mol
D) 0.78 mol
E) 1.34 mol