I have four questions about finite automata like these:
This is what I thought (I do not know it is correct or not):
(a) $L(M)$ is a set of strings which each of the string that the numbers of $1$ in the end is a multiple of $3$.
(b) $2$
(c) $5$
(d) I have no idea.
Can someone help me to solve these questions? Thank for your help.