YES
(VAR x)
(RULES
b(x) -> d(d(x))
a(x) -> d(d(d(d(x))))
c(d(x)) -> d(d(d(d(x))))
e(d(x)) -> d(d(d(d(e(x)))))
e(c(x)) -> d(d(d(d(e(x)))))
d(d(d(d(d(x))))) -> d(d(d(d(x))))
c(c(x)) -> d(d(d(x)))
d(d(d(c(x)))) -> d(d(d(d(x))))
)