During the spring and summer, a concession stand at a community Little League baseball game field sells soft drinks and other refreshments. To prepare for the season, the concession owner refers to the previous year’s files, in which he had recorded the daily soft drinks sales (in gallons) and the average daily temperature (in degrees Fahrenheit). Using the coordinates of the two points (84,80) and (74,65), determine the slope of the line of best fit.