YES(?,PRIMREC) We are left with following problem, upon which TcT provides the certificate YES(?,PRIMREC). Strict Trs: { prime(0()) -> false() , prime(s(0())) -> false() , prime(s(s(x))) -> prime1(s(s(x)), s(x)) , prime1(x, 0()) -> false() , prime1(x, s(0())) -> true() , prime1(x, s(s(y))) -> and(not(divp(s(s(y)), x)), prime1(x, s(y))) , divp(x, y) -> =(rem(x, y), 0()) } Obligation: innermost runtime complexity Answer: YES(?,PRIMREC) The input was oriented with the instance of'multiset path order' as induced by the precedence prime > 0, prime > false, prime > prime1, prime > and, prime > not, prime > divp, prime > =, prime > rem, s > 0, s > false, s > prime1, s > and, s > not, s > divp, s > =, s > rem, prime1 > 0, prime1 > false, prime1 > and, prime1 > not, prime1 > divp, prime1 > =, prime1 > rem, true > 0, true > false, true > prime1, true > and, true > not, true > divp, true > =, true > rem, and > 0, and > false, and > =, and > rem, not > 0, not > false, not > =, not > rem, divp > 0, divp > false, divp > =, divp > rem, prime ~ s, prime ~ true, 0 ~ false, 0 ~ =, 0 ~ rem, false ~ =, false ~ rem, s ~ true, and ~ not, and ~ divp, not ~ divp, = ~ rem . Hurray, we answered YES(?,PRIMREC)