The linear graph shows the possible combinations of cakes and pies a club must sell to meet their fundraising goal. What is the domain of the graph? A) {x: 0 < x < 40} B) {x: 0 ≤ x ≤ 40} C) {x: 0 < x < 20} D) {x: 0 ≤ x ≤ 20}