A parent is buying two types of chocolate truffles for the children. The oldest child likes white chocolate (W), the younger two like dark chocolate (D) and the spouse likes white chocolate (W). Three white chocolate truffles (W) cost the same as two dark chocolate truffles (D). If the parent bought 5 white chocolate truffles (W) and 10 dark chocolate truffles (D), and spent $60.00, how much was each dark chocolate truffle? Calculate the cost of dark chocolate truffles