Im not sure if my formula is wrong or what im doing wrong but id greatly appreciate help for step 4.

Mohave Corp. makes several varieties of beach umbrellas and accessories. It has been approached by a company called Lost Mine Industries about producing a special order for a custom umbrella called the Ultimate Shade (US). The special-order umbrellas with the Lost Mine Company logo would be distributed to participants at an upcoming convention sponsored by Lost Mine. Lost Mine has offered to buy 3,000 of the US umbrellas at a price of $28 each. Mohave currently has the excess capacity necessary to accept the offer. The following information is related to the production of the US umbrella: Direct materials $12.00 Direct labor 7.00 Variable manufacturing overhead 8.50 Fixed manufacturing overhead 2.50 Total cost $30.00 Regular sales price $36.00 Required: 1. Compute the incremental profit (or loss) from accepting the special order. Answer is complete and correct. Profit (or Loss) Increases by 1,500 2. Should Mohave accept the special order? O No Yes 3. Suppose that the special order had been to purchase 3,500 umbrellas for $26.00 each. Recompute the incremental profit (or loss) from accepting the special order under this scenario. Answer is complete and correct. Profit (or Loss) Decreases by 5,250 3. Suppose that the special order had been to purchase 3,500 umbrellas for $26.00 each. Recompute the incremental profit (or loss) from accepting the special order under this scenario. Answer is complete and correct. Profit (or Loss) Decreases by 5,250 4. Assume that Mohave is operating at full capacity. Calculate the special-order price per unit at which Mohave would be indifferent between accepting or rejecting the special order. Answer is complete but not entirely correct. Special Order Price $ 31,500 per Unit