Lucy needs to buy some organic apples, and her grocery store is having a sale on them. If she buys 3 or fewer pounds of apples, the price will be $1.50 per pound. If she buys more than 3 pounds of apples, the price is $1.10 per pound. What is the domain of the piecewise-defined function, where x represents the number of pounds of apples?
A) {x| x ≥ 0}
B) {x| x is a real number}
C) {x| 0 ≤ x ≤ 3}
D) {x| x ≥ 3}