A cardiologist designs a study to examine factors related to the condition of the heart for patients 50 years of age or older. The design obtains physiological information on hundreds of patients. The cardiologist creates an heart health index, HHI, which is an overall assessment of heart health with values ranging from 0 (very poor condition) to 10 (excellent condition). The goal of the study is to obtain a model that will relate (predict) HHI to the following explanatory variables: A, age; BMI, body mass index; E, hours of exercise per week; and SB, systolic blood pressure reading. Write a first- order regression model relating HHI to the four explanatory variables.