Because 3, 4 and 5 are pairwise coprime, their least common multiple is the product of 3, 4 and 5.

So the least common multiple of 3, 4 and 5 is 3×4×5=60.

In other words, the minimum interval between meetings in the library is 60 days.

A: We will meet in the library at least 60 days later.