(a)

There is a city with a population of exactly 5 million people.

In this city, 9 languages are spoken, and each language has exactly 1 million speakers.

Find the least value of N such that there must exist a pair of languages with at least N speakers in common.

(b)

There is a city with a population of exactly 5 million people.

In this city, 16 languages are spoken, and each language has exactly 1 million speakers.

Find the least value of N such that there must exist a trio of languages with at least N speakers in common.