Hi Chris,
Unfortunately it's rare that a school simply asks for a "letter:, it's often a series of questions that get longer answers from the writer. Most likely you will have to ask the writer to write multiple letters. Some recommenders will indeed only write one, in which case you should secure a very comprehensive letter and recognize that you can submit it but the school may find certain pieces of info are lacking. It may be worth exploring alternate recommenders. Also you mention you are looking at academic recommenders -- MBA programs usually specify that they want professional references.
Best of luck,
Daniel Richards
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