<image>As shown in the figure, the amount paid \( y \) (in yuan) and the purchase amount \( x \) (in kilograms) are represented by the function graph consisting of the line segment \textit{\( OA \)} and the ray \textit{\( AB \)}. Therefore, buying 3 kilograms of these apples in one go saves ________ yuan compared to buying 1 kilogram of these apples on three separate occasions.
