MAYBE
Input TRS:
    1: f(x) -> a() | a() --> x
    2: f(x) -> b() | b() --> x
Infeasibility test:
    a() --> x
    b() --> x
Co-Order(NegReal,≥,Sum) ...Co-QLPOpS ...Co-QWPOpS(PosReal,>,Sum) ...Co-Order(PosReal,≥,Sum-Sum; PosReal,≥,Sum-Sum) ...failed.