Hi, I need help with this problem. I know that if 4 coins are flipped there would be 2^4 is 16 which makes there 16 possible outcomes for this problem. I don't get how the answer has 11 outcomes listed. Thanks in advance.

Use a tree diagram showing all possible results when four fair coins are tossed. Then list the ways of getting the indicated result. at least two tails hhitt, huht, huh, hitt. that. thth. thet, tthhutht, tith, titt hutt, thtt, ttht, tith, tutt Chatt, htht, hett, thht. thth, tthhttpt, ttth, titt hhtt, heht, htth, that, thth, tthh