A town has seats for 20 people where it is 4 rows with 5 seats each. When Tim, tam, low, law and wei went in the hall, the seats are empty.

A) determine the number of ways of seating, Tim, tam, low, law, and wei if there is no restriction

B) how many possible ways of sitting if Tim, tam, low are sitting in the back row and law and wei sit together at the other rows?