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(a) The total number of all possible combinations of numbers in this case is = 38416.
It is because there are 14 possible independent opportunities in each of 4 positions.
(b) The probability that every (any) fixed concrete combination will open the lock is therefore = .
The probability that the combination {1-2-3-4} is the happy key is therefore also = .
(c) If you try 25 different combinations of 4 numbers, the probability to open the lock is = .
I answered ALL YOUR QUESTIONS.
Do not forget to post your "THANKS" to me immediately after reading my post.
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By the way, this problem came to the forum some days ago, and I answered and solved it under this link
https://www.algebra.com/algebra/homework/word/misc/Miscellaneous_Word_Problems.faq.question.1139207.html
https://www.algebra.com/algebra/homework/word/misc/Miscellaneous_Word_Problems.faq.question.1139207.html
What is or what was the need to post it again ?