1. Download the dataset titled Invoice.xls from the textbook. An accountant for a large department store has the business objective of developing a model to predict the amount of time it takes to process invoices. Data are collected from the past 32 working days, and the number of invoices processed and completion time (in hours) are stored. (a) Assuming a linear relationship, use the least-squares method to calculate the re- gression coefficients. (b) Use the prediction line developed in (a) to predict the mean amount of time it would take to process 150 invoices.