Tracy works at North College as a math teacher. She will be paid $900 for each credit hour she teaches. During the course of her first year of teaching, she would teach a total of 50 credit hours. The college expects her to work a minimum of 170 days (and less and her salary would be reduced) and 8 hours each day.

What is her gross monthly income?

$75
$900
$3,750
$45,000