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