XYZ Company incurred the following costs for the month of August when it observed an activity level of 5,000 units: Variable costs $32,500; Fixed costs $25,000; Mixed costs $21,500; Total costs $79,000. During October, the activity level was 16,000 units, and the total costs incurred were $178,000. If the activity level were expected to be 9,000 units for the month of December, what amount of total costs would be expected? Select one: a. $124,000 b. $133,000 c. None of the answers given d. $115,000 e. $142,000