Bicycle license plates in Flatville each contain three letters. The first is chosen from the set ${C,H,L,P,R}$, the second from ${A,I,O}$, and the third from ${D,M,N,T}$. When Flatville needed more license plates, they added two new letters. The new letters may both be added to one set or one letter may be added to one set and one to another set. What is the largest possible number of ADDITIONAL license plates that can be made by adding two letters?
Flatville的自行车车牌每个包含三个字母。第一位从集合${C,H,L,P,R}$选,第二位从${A,I,O}$选,第三位从${D,M,N,T}$选。为了需要更多车牌,他们添加了两个新字母。新字母可都加到一个集合,或各加到一个集合。添加两个字母能制造的最大可能新增车牌数是多少?