Incremental Costs and Benefits

Crafty Tools manufactures an electric motor that is uses in several of its products. Management is considering whether to continue manufacturing the motors or to buy them from an outside source. This is the following information that is available.

1-The company needs 10,000 motors per year. The motors can be purchased from an outside supplier at a cost of $20 per unit.
2-The unit cost of manufacturing the motors is $42 computed as follows:

Direct materials $96,000
Direct labor 120,000
Factory overhead:
Variable 90,000
Fixed 114,000
Total manufacturing costs $420,000
Cost per unit ($420,000 divided 10,000 units) $42

3-Discontinuing the manufacture of motors will eliminate all the raw materials and direct labor costs but will eliminate only 75% of the variable factory overhead costs.
4-If the motors are purchased from an outside source machinery used in the production of motors will be sold at its book value. Accordingly no gain or loss will be recognized. The sale of this machinery will also eliminate $4,000 in fixed costs associated with depreciation and taxes. No other reductions in fixed factory overhead will result from discontinuing the production of motors.

Now this is where I need the help:
A. Prepare a schedule to determine the incremental cost or benefit of buying the motors from the outside supplier. Would you recommend that the company manufacture the motors or buy them from the outside source?

B. Assume that if the motors are purchased from the outside source the factory space previously used to produce motors can be used to manufacture an additional 7,000 power trimmers per year. Power trimmers have an estimated contribution margin of $10 per unit. The manufacturer of the additional power trimmers would have no effect on fixed factory overhead. Would this new assumption change your recommendation as to whether to make or buy the motors? In support of your conclusion prepare a schedule showing the incremental cost or benefit of buying the motors from the outside source and using the factory space to produce additional power trimmers.

This is a problem I need help with. Thank you.