For each n people, Margie bought a hamburger and a soda at a restaurant. For each of n people, Paul bought 3 hamburgers and a soda at the same restaurant. If Margie spent a total of $5.40 and Paul spent a total of $12.60, how much did Paul spend just for hamburgers? (Assume that all hamburgers cost the same and all sodas cost the same)

A) $10.80

B) $9.60

C) $7.20

D) $3.60

E) $2.40