How many blue rams can a 40 gallon aquarium hold?

I have a planted forty gallon aquarium (open top) with lots of hiding places. It already has 2 powder blue dwarf gouramis. I would like to add 1 red tail shark, 10 cardinal tetra, 1 small plec and 6 corydoras. The other fish i would like to add is a blue ram. How many can my aquarium hold? I was thinking about having three.