Suppose I have a model that predicts customer interest based on a customer's age (a number), the amount of advertising (a number) to which they have been exposed, and in which of four geographical regions they reside. This last piece of information is a category. Please describe how we can incorporate this category into a multiple linear regression using "dummy variables". Customer ID Age Advertisement Region 001 40 22 NE 002 35 5 S 003 56 18 S 004 21 0 MW 005 34 7 W 006 40 18 S 007 18 44 NE