a designer studio offers custom design work for printed and electronic media.The studio expects to bill out 4,200 billable hours in one quarter.Design work for printed media typically makes up about 20% of total billable hours and revenue,while design work for electronic media makes up the rest.Design work for printed media is billed at $450 per hour, and design work for electronic media is billed at $300 per hour.Variable costs amount to 45% of the hourly rate for both.

During the latest quarter , 4,050 hours were actually billed out, with design work for printed media taking up 15% of all billings.What is the total sales mix varaince