Sales of$$ Volkswagen's popular Beetle have grown steadily at auto dealerships in Nevada during the past $5$ years$($see table$$ below$).$

$$

Year

Sales

$1$

$2$

$3$

$4$

$5$

Part $2$

$$a$)$ Forecasted sales for year $6$ using the trend projection$($linear regression$)$ method are

$$

$613\mathrm{.}7$ sales $($round your response to one decimal$$ place$).$

Part $3$

$$b$)$ The MAD for a linear regression forecast is

$$

$6\mathrm{.}2$ sales $($round your response to one decimal$$ place$).$

Part $4$

$$c$)$ The MSE for the linear regression forecast is

$$

$65\mathrm{.}7$ sales $($round your response to one decimal$$ place$)$