Solution :
Base year : 2019
Expenditure on crackers : $44
Expenditure on bandages : $12
Price of a firecracker : $1
Price of bandages : $3 per pack
Number of crackers bought =
= 44
Number of bandages bought = 
= 4
Total expenditure in 2019 = $44 + $12
= $56
Year 2020
Price of a firecracker = $6
Price of a bandage = $3
Expenditure on the crackers = $ 6 x 44
= $ 264
Expenditure on the bandages = $ 3 x 4
= $ 12
Total expenditure in 2020 = $ 264 + $ 12
= $ 276
CPI in the year 2020 (base year 2019) = 
= 492.8
Inflation in 2020 (2019 base year = 100) = 
= 0.039
= 3.9%
So, CPI = 492.8
Inflation rate = 3.9%