愁死了，小三数学题怎么做？在线等指教！

Candice makes gift boxes during her free time.
She charges 40 cents for a triangular box, 50cents for a heart-shaped box and 60 centss for a cylindrical box.
Last sunday, she sold 16 diffierent types of gifts boxes and collected a total of $8.
How many of each type of box did she sell?
　
受不了，文科生太费脑。求各路高手指教。