In working for a local retail store, you have developed the following estimated regression equation:

where:
y = Weekly sales
x1 = Local unemployment rate
x2 = Weekly average high temperature
x3 = Number of activities in the local community
x4 = Average gasoline price
a. Interpret the values of b1, b2, b3, and b4 in this estimated regression equation.
b. What is the estimated sales if the unemployment rate is 5.7%, the average high temperature is 61°, there are 14 activities, and gasoline average price is $3.39?