The Demand for Ballard's Glass Company's Products Varies, Ranging from 10

The demand for Ballard's Glass Company's products varies, ranging from 10 to 20 windows a day with an average of 15. John Ballard works eight hours a day, five days a week. Each order is one window, and each window takes 26 minutes to install. The company plans to add doors to its product line and anticipates that they will sell an average of 5 doors per day. Each door takes 12 minutes to install. Ballard is concerned with the increased waiting time if it adds doors. To offset this concern it can hire a part-time employee. This will decrease windows time to 20 minutes and doors to 10 minutes. However, this will increase the costs of windows from $10 to $12 and doors from $6 to $7.50. Since he is giving customers faster service he will increase his prices from $17 to $20 for windows and from $10 to $12 for doors.
What is the daily contribution margin if he sells both windows and doors and the part-time person is hired?

A) $185.00
B) $142.50
C) $140.00
D) $97.50
E) $72.00