Kayson mixes 300 milliliters ( mL ) (mL) of spinach, 200mL of berries, and 42mL of dressing to make a salad. There are s s milligrams ( mg ) (mg) of vitamin C per milliliter of spinach, b mg bmg per milliliter of berries, and d mg dmg per milliliter of dressing. Which expressions can we use to describe how many milligrams of vitamin C are in the salad?