Michelle (CEO) and Brian (President of Sales) are arguing about the sales forecast for 2023. Brian proposed a simple time series analysis to forecast sales. Michelle was pushing for a multiple regression technique (Index #1 and Index #2) to forecast sales.

Part A: Develop monthly sales forecast for Jan 2023 to Jun 2023 based on both Brian and Michelle's approaches.

Part B: As an independent consultant which option do you recommend? Briefly explain your rationale.

\begin{tabular}{|r|r|r|r|} \hline \multicolumn{1}{|l|}{ Month } & \multicolumn{1}{l|}{ Sales } & \multicolumn{1}{l|}{ Index \#1 } & Index \#2 \\ \hline Jan-22 & 90 & 1000 & 280 \\ \hline Feb-22 & 80 & 980 & 275 \\ \hline Mar-22 & 95 & 985 & 290 \\ \hline Apr-22 & 75 & 970 & 250 \\ \hline May-22 & 95 & 985 & 299 \\ \hline Jun-22 & 70 & 940 & 240 \\ \hline Jul-22 & 90 & 955 & 270 \\ \hline Aug-22 & 75 & 935 & 250 \\ \hline Sep-22 & 70 & 930 & 245 \\ \hline Oct-22 & 75 & 938 & 255 \\ \hline Nov-22 & 85 & 975 & 265 \\ \hline Dec-22 & 80 & 960 & 260 \\ \hline Jan-23 & & 960 & 255 \\ \hline Feb-23 & & 965 & 260 \\ \hline Mar-23 & & 945 & 240 \\ \hline Apr-23 & & 940 & 235 \\ \hline May-23 & & 980 & 250 \\ \hline Jun-23 & & 990 & 275 \\ \hline \end{tabular}