Ivanhoe Street Inc. makes unfinished bookcases that it sells for $57. Production costs are $37 variable and $10 fixed. Because it has unused capacity, Ivanhoe Street is considering finishing the bookcases and selling them for $75. Variable finishing costs are expected to be $8 per unit with no increase in fixed costs. Prepare an analysis on a per unit basis showing whether Ivanhoe Street should sell unfinished or finished bookcases. (Enter negative amounts using either a negative sign preceding the number eg. 45 or parentheses eg. (45)