Please help me AGAIN with these questions and try to give me the correct answers with explanations. Thank you

Please help me with those questions only, I resolved the 1-3. And if you can explain the steps ..thank you!

The contribution format income statement for Huerra Company for last year is given below:

	Total		Unit
Sales	$	994,000	$	49.70
Variable expenses		596,400		29.82
Contribution margin		397,600		19.88
Fixed expenses		313,600		15.68
Net operating income		84,000		4.20
Income taxes @ 40%		33,600		1.68
Net income	$	50,400	$	2.52

The company had average operating assets of $504,000 during the year.

4. The company issues bonds and uses the proceeds to purchase $125,000 in machinery and equipment at the beginning of the period. Interest on the bonds is $14,000 per year Sales remain unchanged. The new, more efficient equipment reduces production costs by $6,000 per year. (Round your answers to 2 decimal places.) Effect Margin Turnover ROI