The president of a small manufacturing firm has been concerned about continual growth in manufacturing cost over the past several years. the following is time series of the cost per unit(in dollars) for the firm's leading product over the past eight years

Year Cost per Unit ($)
1 20.00
2 24.50
3 28.20
4 27.50
5 26.60
6 30.00
7 31.00
8 36.00

a.Graph this time series. Does a linear trend appear?

b. develop the equation for the linear trend component for the time series. What is the average cost increase per year?