Timothy bought groceries two days during the week.

timothy purchased $11.25 worth of groceries and paid $12.15
after taxes on monday.
timothy paid $59.13 after taxes on a purchase of groceries that
cost $54.75 on friday.

which equation models the relationship between y, the cost of groceries after taxes, and x, the cost of groceries before taxes?

a: y= 0.09x

b: y= 1.08x + 0.09

c: y= 0.9x + 12.15

d: y= 1.08x