YES(?,ELEMENTARY)

'epo* (timeout of 60.0 seconds)'
--------------------------------
Answer:           YES(?,ELEMENTARY)
Input Problem:    innermost runtime-complexity with respect to
  Rules:
    {  and(tt(), X) -> X
     , plus(N, 0()) -> N
     , plus(N, s(M)) -> s(plus(N, M))
     , x(N, 0()) -> 0()
     , x(N, s(M)) -> plus(x(N, M), N)}

Proof Output:    
  Strict Rules in Predicative Notation:
   {  and(; tt(), X) -> X
    , plus(0(); N) -> N
    , plus(s(; M); N) -> s(; plus(M; N))
    , x(N, 0();) -> 0()
    , x(N, s(; M);) -> plus(N; x(N, M;))}
  Safe Mapping:
   safe(and) = {1, 2}, safe(tt) = {}, safe(plus) = {1}, safe(0) = {},
   safe(s) = {1}, safe(x) = {}
  Argument Permutation:
   mu(and) = [2, 1], mu(plus) = [1, 2], mu(x) = [1, 2]
  Precedence:
   x ~ x, x > plus, x > and, plus ~ plus, plus > and, and ~ and