add prices depending on the room occupancy

Hello.

I want to ask how to add diferrent prices to the room types i have on my property profile.

For example i have a triple room and i want to make a price for 2 persons and a price for 3 persons. I also have a double room that i want to post a price for 1 person(single use) and i can do it from the system. So i was wondering why i cannot do it to the other types as well. During the procedure, a window shows up with the choices for putting prices for  2 or three persons but it doesnt let you do something. 

Thank you in advance for your help.