math problem !?

Gift cards have increased in popularity in recent years. Consumers appreciate gift cards because they get to select the present they like. The U.S. sales of gift cards (in billions of dollars) is approximated by
S(t) = −0.6204t3 + 4.671t2 + 3.354t + 47.4 (0 ≤ t ≤ 5)
in year t, where t = 0 corresponds to 2003.†

(a) What were the sales of gift cards for 2003?
__________$ billion

(b) What were the sales of gift cards for 2004?
___________$ billion