A local car wash company has discovered that the less they charge for car washes the more washes they sell. Over several weeks they experiment with different prices. The results were averaged and graphed below. 

a. Estimate the slope of the line by carefully approximating the ordered pairs for two points. Pick points that are fairly far apart for a better estimate. 

b. What are the units associated with the slope? What does the slope tell you about the problem? 

c. You may notice that the graph does not show any intercepts. What would the vertical intercept mean? What would the horizontal intercept mean?