I waited in line at McDonald's for a while, so I had time to ponder this sign. The first mistake I noticed was the incorrect use of "quicker." Because this word is working to modify the verb "can serve" and answers the question how, it is an adverb. It should read "quickly" or "more quickly." My astute English teacher friends pointed out that there should be a comma before the conjunction "so" because the conjunction joins two independent clauses. (That means two word groups that could stand alone.)
