Loop of length 7 starting with a string of length 4
found after enumerating 105 derivations:

.bb.aa
	rule bb -> c at position 0
.c.aa
	rule ca -> aabaac at position 0
.aabaac.a
	rule a ->  at position 3
.aabac.a
	rule a ->  at position 3
.aabc.a
	rule ca -> aabaac at position 3
.aabaabaac.
	rule a ->  at position 3
.aababaac.
	rule a ->  at position 3
.aabbaac.