Loop of length 7 starting with a string of length 4
found after enumerating 43 derivations:

.ba.ca
	rule ba -> abbcaa at position 0
.abbcaa.ca
	rule a ->  at position 4
.abbca.ca
	rule a ->  at position 4
.abbc.ca
	rule cc ->  at position 3
.abb.a
	rule ba -> abbcaa at position 2
.ababbcaa.
	rule b ->  at position 3
.ababcaa.
	rule b ->  at position 3
.abacaa.