Suppose a student started a chain email by sending the message to 3 friends and asking those friends to each send the same email to 3 more friends exactly 1 day after they received it.

Representation: Write an explicit formula for the sequence that models the number of people who will receive the email on the ℎ day. (Let the first day be the day the original email was sent.) Assume everyone who receives the email follows the directions. SHOW WORK.