I am lost on the usage of inquire. Are any of the following sentences acceptable? If so, which is the most appropriate?
- I'd like to inquire if you are still accepting applications?
- I'd like to inquire as to if you are still accepting applications or not?
- I'd like to inquire whether you are currently accepting applications.
This is part of a formal letter and I am held up on how to correctly write this sentence. This question is is similar to this question.