A mail-order firm has found the following seasonal indexes for the number of calls received each month. Below the seasonal indexes is the actual number of calls (thousands) per month during 2005.
a. Using the seasonal indexes, deseasonalize the data for 2005.
b. The president of the firm is quite pleased that the number of calls went up each month during the May through December portion of 2005. Based on the results obtained in part (a), is the firm's performance really on the increase?