Answer:
The number of arrangements is equal to 
Step-by-step explanation:
The multiplication principle states that if a first task can be done in n1 different ways, a second task can be performed in n2 different ways... and extending this logic for i tasks gives us the total ways as
n1 x n2 x... x ni
Moreover, with n-elements arranged in a line, the total arrangements possible are n! which is referred to as n-factorial.
As an example: If we wish to arrange 4 distinct items in a row.
The total ways to arrange this is
ways.
Applying the multiplication principle and n-factorial number:
The number of ways to line up all 40 for a photograph, with all 12 sophomores to the left, all 8 juniors in the center, and all 20 seniors to the right is: The total configurations for the 12 sophomores in a row multiplied by the arrangements for the 8 juniors and finally multiplied by the total ways to align all 20 seniors in a row ⇒ 