PLan A = 420 + 0.09 x
Plan B = 696 + 0.05 x
Where: x = sales amount
If A is better than b
A > B
420 + 0.09 x > 696 + 0.05 x
Solve for x
0.09x- 0.05x > 696 - 420
0.04x > 276
x > 276 / 0.04
x > 6,900
Chris should select plan A for sales greater than $6,900