A collation of two strings s and t is an interleaving of the letters of the two strings that preserves the relative order of the letters within each string. For example, the strings LID and ALE admit the following collations: ALLIDE, LIDALE, ALLIED, LIALDE, among others.

A. What are the minimum and maximum number of different collations of two strings s and t?

B. What is the maximum number of different collections of three strings r, s, and t?