Linear regression was used to develop the slope and intercept values for a forecast equation in Y (sales volume) and X (customer traffic) using the data below (sales in million dollars; customers in thousands). Forecast the sales volume when the customer level is 22. a = -0.158; b = 0.131

\begin{tabular}{llllllll} \hline Customers (X) & 10 & 12 & 16 & 15 & 14 & 17 & 20 \\ \hline Sales Volume (Y) & 1.0 & 1.4 & 1.9 & 2.0 & 1.8 & 2.1 & 2.3 \\ \hline \end{tabular}