Coupled Inductor Circuit Simplification

[Etesla]

Fun math problem if you're into that sort of thing. Can anyone figure out how to do this transformation? I'm starting with 4 inductors and some parameters L12, L34, and K. I want to transform that circuit into a simpler one with only two inductors and one coupling statement. So basically can anyone solve for A, B, and C in terms of L12, L34, and K?
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