The total revenue desired is

revenue = (cost) + 20%*(cost) = 1.20*(cost) = 1.20*($1.58/gal)*(30 gal) = $56.88

The amount of milk available for sale is

(gallons for sale) = (original amount of milk) - 15%*(original amount of milk)

= 0.85*(30 gal) = 25.5 gal

The selling price per gallon must be

selling price = $56.88/(25.5 gal) ≈

The formula ends up being

selling price/gal = (cost/gal)*(1+markup on cost)/(1 - spoilage rate)

= $1.58*1.20/0.85

revenue = (cost) + 20%*(cost) = 1.20*(cost) = 1.20*($1.58/gal)*(30 gal) = $56.88

The amount of milk available for sale is

(gallons for sale) = (original amount of milk) - 15%*(original amount of milk)

= 0.85*(30 gal) = 25.5 gal

The selling price per gallon must be

selling price = $56.88/(25.5 gal) ≈

**$2.23/gal**The formula ends up being

selling price/gal = (cost/gal)*(1+markup on cost)/(1 - spoilage rate)

= $1.58*1.20/0.85