Mr. Jackson orders lunches to be delivered to his workplace. The cost of each lunch is $5.25, with a one-time delivery fee of $2.25. What expression could Mr. Jackson use to find the cost of ordering n lunches?
A. 5.25n + 2.25
B. 7.50n
C. 3n + 2.25
D. 5.25 + 2.25n