What strings are accepted by the pattern "^[ab]?|c?$"?

Question

What I have gathered till now:

1. ^ -> match the first symbol
2. $ -> match the last symbol
3. [] -> set of characters that can be in the position
4. | -> the "OR" operator
5. ? -> the previous condition is optional

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What I think the pattern means:
The line has to either begin with an a or a b or has to end with a c or has to be an empty string. I am having trouble drawing the dfa for the pattern though. What's throwing me off is the "optional" symbol. I am not able to understand what strings won't be accepted in the language.

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Can someone point me in the right direction?

Answer 1

^ matches the start of the line.

[ab]? matches "a", or "b", or nothing.

c? matches "c", or nothing.

$ matches the end of the line.

So, I think these lines will match:

(empty line)
a
b
c