Answer and Explanation:
The computation is shown below:
Total fixed costs is 
= depreciation + advertising + insurance 
= 1224 + 153 + 1683 
= $3060 per month 
Now 
Total variable cost per unit 
= weed + direct labor + fuel 
= 10 + 8 + 2 
= $20/ per lawn 
Now 
Contribution margin ratio = (sales per unit - variable cost per unit) ÷ sales per unit 
= ($50 - $20) ÷ 50 
= 60% 
 Now 
Breakeven sales is 
= fixed costs ÷ contribution margin ratio 
= $3,060 ÷ 60% 
= $5100 
 And, 
Breakeven sales units is 
= breakeven sales ÷ sales per unit 
= 5100 ÷ 50 
= 102 lawns