Since each plan has the same profit of $2000 there is no combination that will maximise your profit, your profit will always be 300*2000-250000
I can give you 1 more constraint though.
You know S+D+E=300 so
And you now know 210=>S+D=>150
edit. I forgot to mention that my notation was D for the number of people buying the deluxe plan, S for standard and E for economy.