when u reach lt commander r u given a new ship or do u have to buy it?

when u reach lt commander r u given a new ship or do u have to buy it?

You can claim it at Sol Station, for free. You can choose either science, escort or cruiser ship, but you can also buy (for about 22,000 credits) another ship if for some reason you want.

you get like one free exchange credit or something which you exchange for a ship of your choice