There are 3 different brands of cements named A, B and C. For a small 6-layer sculpture, Leo needs 6 bags of cements. Leo doesn't know that A is a good quality cement brand, B is of average quality and C is a poor quality cement brand. If Leo uses at least 1 bag of cement C, the sculpture will collapse. Using more than 2 bags of cement B results the same. Else, the sculpture will last longer) If it is equally likely for him to use all 3 brands, what is the probability that the sculpture will last and won't collapse?