Answer:
One pound costs 1.26, two costs 1.47, three costs 1.68, and four costs 1.89. So we calculate how much it increases in each pound.
1.26 + 21 = 1.47
1.47 + 21 = 1.68
1.68 + 21 = 1.89
1.89 + 21 = 2.10
2.10 + 21 = 2.31
2.31 + 21 = 2.52
2.52 + 21 = 2.73
8 pounds cost: 2.73
So I pay $ 2.73 for 8 pounds.
