Problem on average retail price and the Consumer Price Index

Question

Table indicate the average retail price of milk and the Consumer Price Index in the year 1980 -1998.

Alter the CPI into 1990 = 100 and find out the real price of milk in the year of 1990 dollars.
To alter the CPI into 1990=100, divide the CPI for each year by the CPI for 1990. Employ the formula from part a & the new CPI numbers below to determine the real price of milk.
          New CPI            1980  63                                                       Real price of milk      1980   $1.67
                                 1985  82                                                                                     1985   $1.38
                                 1990  100                                                                                   1990   $1.39
                                 1995  117                                                                                   1995   $1.26
                                 1998  125                                                                                   1998   $1.29