Nelson Industries manufactures a part for a type of aircraft engine that is becoming obsolete. The sales history for the last 10 years is as follows:

Year	Dec-08	Dec-09	Dec-10	Dec-11	Dec-12	Dec-13	Dec-14	Dec-15	Dec-16	Dec-17
Sales	945	875	760	690	545	420	305	285	250	210
Time	1	2	3	4	5	6	7	8	9	10

a). Plot sales versus time.

b). Estimate the regression model for a linear time trend of sales.

c). What is the mean absolute percent error of the linear regression estimates for these 10 years?

d). Using this model, estimate sales for year 11.