Quantities and prices of these goods for the last several years are shown in the following table. The base year is 2015.

Year	Cereal	Milk
Price (Dollars per box)	Quantity (Boxes of cereal)	Price (Dollars per gallon)	Quantity (Gallons)
2015	4.00	100	1.50	180
2016	4.00	120	2.00	200
2017	5.00	150	2.50	200
2018	6.00	180	3.50	240