Answer was D) I believe but I need exact help with steps on how to solve, as I usually ask, please show detailed help with steps, and show how #'s are added/multiplied/divided to get to final answer.

The Post Division of the Woodhead Company produces basic posts which can be sold to outside customers or sold the Wood Division of the Woodhead company. Last year, the Lamp Division bought all of its 25,000 posts from the Post Division. The following data are available for last year's activities of the Post Division :

Capacity in Units : 300,000

Selling Price Per Post to Outside Customers : $1.75

Variable Costs Per Post : $0.90

Fixed Costs Total : $150,000

Suppose the transfers of posts to the Lamp Division cut into the sales of the Post Division to outside customers by 15,000 units. Further, suppose that an outside supplier is willing to provide the Lamp Division with basic posts at $1.45 each.

Question : If the Lamp Division had chosen to buy all of its posts from the outside supplier instead of Post Division, the change in net operating income would have been? A) 1,250 decrease B) 10,250 increase C) 1,000 decrease D) 13,750 decrease E) none

Thanks