Given the model below: Period 1 2 3 4 5 6 7 8 9 10 11 Demand 110 140 170 160 130 130 170 160 140 180 220 Oil 90 83 62 93 71 92 68 64 90 61 40 price so picture Click here for the Excel Data File a. Compute the forecast for period 12 using a causal regression model and assuming that oil price for period 12 is 85. (Round regression coefficients and forecasts of demand to two decimal places.) Forecast for period 12 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.) Largest error is in period