<image>Lao Wang purchased some kilograms of watermelon from the wholesale market at a price of 0.8 yuan per kilogram to sell at the market. After selling some of the watermelons, the remaining watermelons had their price reduced by 0.2 yuan per kilogram. After selling all the watermelons, the relationship between the total sales amount and the number of kilograms sold is shown in the diagram. How much did Lao Wang earn (_____ )
