Production overheads costs at company VW are assumed to vary with the number of machine hours worked, A line of best fit will be calculated from the following historical data, with costs adjusted to allow for costs inflation over time.

Year	Total production overheads	Number of machine hours	Cost index
2018	$ 143, 040	$ 3,000	192
2019	156,000	3,200	200
2020	152,320	2,700	224
2021	172,000	3,000	235

a. Calculate the cost in 2021 terms.

b. Use in your answer to calculate the line for the best fit using method.

c. Calculated expected total overhead cost in 2020 if the machine worked is $3100 and the cost index is 250.