makubexho, The word 'use' can be countable or uncountable, so it can be used with our without the article. It also has two definitions that apply to your cover letter: 1) the act of using or the act of using with some aim or purpose. 2) the habitual, usual, or common use ( "the" is always used with this definition because it is a specific kind of use) 2) If you are talking about common usage of Excel, you need the article "the" to communicate this idea. Example: The post also involved the use of Excel for rebate and sales revenue computation. However, since you added the adjective "extensive", it is no longer a question of common usage. We are now talking about extensive usage. Definition 2) does not fit your sentence. 1) So now you have to decide: Is "the extensive use" of Excel countable or nouncountable? Countable: an extensive use of Excel among the possible uses of Excel? There were five extensive uses of Excel in my work with the post this year. There were two extensive uses of Excel this year, the one in my work with the post and the one in my general workplace. The post also involved an extensive use of Excel for rebate and sales revenue computation. By using "the" instead of "an" you are assuming that the reader understands the reference to "THE extensive use of Excel". Because you don't know who will read the cover letter, your use of "the" is not warranted. The post also involved the extensive use of Excel for rebate and sales revenue computation. We are left with only one logical alternative: In your cover letter "use" should be an uncountable noun. Why? Because you are not talking about common use or countable use. You are speaking of "extensive use" as a general uncountable activity. The post also involved extensive use of Excel for rebate and sales revenue computation.

In order to see why Cherry is correct, try the sentence without the adjective "extensive". "The job also involved use of Excel." - Sounds a little too short and awkward doesn't it? "The job also involved the use of Excel." - Sounds more correct. Just add "extensive" and you have your answer.

I stand by my original answer in this case. I just don't think this paragraph "flows" with the article "the" inserted in that position. Also, you may wish to rephrase the following: "Other office duties are but not limited to filing documents, photocopying, faxing, internal inventory auditing and so forth." Something like this would be better: "Other office duties include, but are not limited to: filing documents, photocopying, faxing, internal inventory, auditing and so forth."

It's a bit of a tricky one. Yes you can do it either way, but at the end of the day you need to see how it fits into the rest of the sentence. As someone else has pointed out, it needs to flow. Try reading it out loud in the complete paragraph to see how it sounds.

You can say either here. You can include the "the'", or you can leave out the"the". Either way is correct.