Which is least expensive per unit of volume? assume the gasoline is $1.94/gallon, soda $1.69/l, and milk $0.89/qt?

To be able to answer this item, we are to convert the price units to a unit that has the same units of measure for the volume. For the purpose of unity, we use gallon as our basis.

For Gasoline: 
  Gasoline :    $1.94 / gal

For Soda:
   Use the conversion factor, 1 gallon = 3.79 L
             Price = ($1.64 /L) x (3.79 L / gal) = $6.22/gal

For Milk:
   Use the conversion factor, 1 gallon  = 4 quarts
             Price = ($0.89/qt)(4 qt / gallon) = $3.56/gallon

The least expensive of the items is the gasoline.