The Shear Madness hair salon operates with an 80% markup on the styling products it sells to its customers. Their planned purchases for the month are 40 shampoos ($36 retail), 40 conditioners ($28 retail) and 30 styling gels ($22 retail). A new vendor offers to sell the salon both shampoo and conditioner for $6 per unit. If the buyer makes this purchase, what is the maximum she can spend per unit on styling gel