The base price, which in this case is taken to be the price from last year. Adding up the prices,
T = $24 + $12 = $36
This year, the total cost, C, is,
C = $30 + $15 = $45
The consumer price index is calculated through the equation,
Price Index = (Current Price / Base Period Price) x 100
Substituting,
Price Index = ($45 / $36) x 100 = 125
ANSWER: 125