Ericka is also in Mr. Whittaker’s science class and she recorded the variation in water level at a different part of the river. She observed that the water level there fell 2.2 millimeters per year over a period of 6.2 years This data is compared to the average annual trend, which shows the water level rising 1.8 mm/year. Which of the decimals in the problem should be represented as a negative rate? Which two factors should Ericka multiply to find the total variation in water level?