The salesperson needs to pack 42 balls in boxes. One type of box can hold 4 balls, and the other type of box can hold 6 balls. If each box must be filled, how many different ways are there?
营业员要把42个球装在盒子里，一种盒子可以装4个，另一种盒子可以装6个，如果每个盒子都要装满，有多少种不同的装法？
<result>3</result>