you are invited to go pick berries in a field with your friends. You have $25 to spend and want to pick 21 pounds of berries. Strawberries are $1.40 a pound raspberries are $1.30 a pound and blueberries are $1.10 a pound. You decide to pick twice as many blueberries and strawberries and raspberries in mind. How many pounds of berries did you purchase