Please note that this letter is merely an inquiry regarding your interest and availability.
Here's why:
* "Note that": This is a common phrase used to introduce a piece of information.
* "merely": This word emphasizes that the letter is only an inquiry, not a formal request or offer.
* "an inquiry": This is the correct word choice to describe a request for information.
* "regarding": This preposition connects the inquiry to the specific topics of interest and availability.
The original sentence had a few grammatical errors:
* "this letter merely": This word order is awkward and unnecessary.
* "an inquiry regarding": This phrase was missing the article "an".
* "your interest and availability": While grammatically correct, it's a bit wordy. "Interest and availability" is a common phrase that can be used together.
The revised sentence is clearer, more concise, and grammatically correct.