Generate the answer for a given question. The question requires common knowledge of English. Make sure that the answer is in detail, long, consistent with the context, and requires general knowledge of English. To be less repetitive, please vary your language for each question. Give a proper explanation to answer, and if necessary, provide the definition of various terms. And conclude your answer if it's long. If you have used other resources (e.g., Merriam Webster's.) to answer the question, include citations in your answer. You don't need to paraphrase the context of your resources, but make sure that your answer is consistent and complete.

Q: The context: Customer pays for some service 100$. If he chooses an option X, we charge him 20$ more, so 120$ in total. As a programmer I want my variables to have meaningful names. How would you call this 20$ in this context? I consider two words: markup (but it is more related to the business than customer IMHO) and surcharge.

A: The words that immediately come to mind are 'surcharge' and 'fee'. Consider the following: Basic cable service provides 50 standard channels for a set price of $30 a month. As for the premium channels, you may order them for an additional surcharge of $20. ...or the following: Standard repair service rate for a computer is $40 an hour. There is, however, an overnight fee of $10 for every night the computer is kept in our possession, after the repair is completed. We notify you after we have completed the service, and for every day that passes, you incur this extra fee. I am just utilizing random numbers on the example sentences, but I hope they help clarify usage.
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Q: I'm a non-native English speaker, and my automatic spellchecker seems to accept both therefore and therefor. Is one orthography preferred ? Is that a British vs. American difference ? Or an old vs. more recent orthography ? Or something else ?.

A: Therefor means for that. For example: Here we sell guitars and accessories therefor. Therefor is one of a whole series of adverbs: thereof (of that), thereafter(after that), therein (in there), etc. If you are familiar with German - the Germanic sister of English - you can find a direct analogy there: for = fur therefor, for that = dafur (literally, therefor) Therefore, as you must know, means as a (logical) consequence
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Q: I have to write this on a website, which one is better? Are you looking for [...](description of our service)? You've come / You came to the right place!.

A:
When you mention something that happened in the past, its timing isn't mentioned and is perhaps no significance to your mention, and you're mentioning it because of its significance in relation to something happening in the present then the present perfect is suitable. In this case, 'You came to the right place' isn't grammatically incorrect, but it doesn't express as explicitly what 'You've come to the right place' does: That, because of your having come here, you are now, in the present, in the right place (to receive good service, to eat a delicious meal, etc.). This use of the present perfect is summarized here.
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