Caryn eamed $5000 working part time as a cashier in a department store. She put her earnings into three different bank accounts. She put some of her money in a checking account paying 5% annual interest, some in a savings account paying 6%, and the rest in a 1-year certificate of deposit paying 7%. The accounts eamed simple interest. No additional money was deposited into or withdrawn from the accounts during the year, and the total interest at the end of the year was $325. If she invested 3 times as much at 6% as at 5%, find the amount she invested at each rate.