Answer
Total cost of labor = 8 hours x $7 = $56
The cost to make party trays is $14 and sold for $35,
∴ Profit per tray = $35 - $14 = $21
Now, to know how many trays must be sold to cover all costs including labor, we divide the total cost of labour by the profit per tray, that is;
$56/$21 = 2.67 trays.