3) When iron pyrite (FeS2) is heated in air, the process known as "roasting" forms sulfur dioxide and iron(III) oxide. When the equation for this process is completed and balanced, using the smallest whole number coefficients, what is the coefficient for "O2"? ___ FeS2 + ___ O2 ___ SO2 + ___ Fe2O3

(a) 11
(b) 7
(c) 8
(d) 4
(e) 2