Measurements on systolic blood pressure, body weight, gender (male or female), and age are recorded for n = 200 people in the 50 to 70-year-old age group. The data will be used to estimate a multiple regression model for predicting systolic blood pressure from four predictors: body weight, gender, age, and an interaction between gender and age. Consider matrix notation for the model. State how many rows and columns there must be in the X matrix and describe the numerical values in each column. Be specific