Random number such that, in [a, b, c], a is 2x likely b, b is 2x likely c. (2x or any abitrary number)

Is there something already built-in .NET (Core v3.1 if that matters) Library to do this? Is there a helpful 3rd party library? Or do I have to do it manually using discrete distribution?

In any case, please advise me the best / cleanest method. Thanks