Loop of length 12 starting with a string of length 7
found after enumerating 55 derivations:

.cbb.bbbb
	rule cbb -> bbbcac at position 0
.bbbcac.bbbb
	rule cbb -> bbbcac at position 5
.bbbcabbbcac.bb
	rule ab -> c at position 4
.bbbccbbcac.bb
	rule cbb -> bbbcac at position 4
.bbbcbbbcaccac.bb
	rule cbb -> bbbcac at position 12
.bbbcbbbcaccabbbcac.
	rule ab -> c at position 11
.bbbcbbbcacccbbcac.
	rule cbb -> bbbcac at position 11
.bbbcbbbcaccbbbcaccac.
	rule cbb -> bbbcac at position 10
.bbbcbbbcacbbbcacbcaccac.
	rule cbb -> bbbcac at position 9
.bbbcbbbcabbbcacbcacbcaccac.
	rule ab -> c at position 8
.bbbcbbbccbbcacbcacbcaccac.
	rule cbb -> bbbcac at position 8
.bbbcbbbcbbbcaccacbcacbcaccac.
	rule cbb -> bbbcac at position 7
.bbbcbbbbbbcacbcaccacbcacbcaccac.