Given the model below:

Period	1	2	3	4	5	6	7	8	9	10	11
Demand	150	160	170	180	180	180	210	190	190	170	250
Oil price	94	95	94	92	61	65	43	82	62	84	45

a. Compute the forecast for period 12 using a causal regression model and assuming that oil price for period 12 is 80. (Round regression coefficients and forecasts of demand to two decimal places.)

b. Create a graph of the gasoline sales and oil price data and include a line representing the regression model. In which period is gasoline sales least well predicted by oil price? What is the amount of this largest error? (Use your rounded regression coefficients and errors from Part a. Round your largest error answer to 2 decimals. Include the negative sign if that largest error is negative.)

Excel File:

Problem 12.22
Period	1	2	3	4	5	6	7	8	9	10	11
Gasoline sales	150	160	170	180	180	180	210	190	190	170	250
Oil Price	94	95	94	92	61	65	43	82	62	84	45