Ten minutes, perhaps less. Use straightforward language. Simple sentences. No Jamesian syntax or vocabulary David Foster Wallace would likely approve of. The tone could either be sad, or it could be self-deprecating. Maybe both.
The story is going to be about friendship. More than that, it is a story about the loss of that friendship.
Writers, especially young writers, new writers, writers who have not had that much experience with the craft, are often advised to write what they know, write stuff about which they can say something, anything. Although on the whole I do not find it an unsound advice—in fact it is a great way to jumpstart the mind, get the juices flowing—I believe there is a better way to go about it. Instead of writing what you do know, write about the things that you don’t. Write not about falling in love, say, but about how that certain someone makes you feel and why you think it is love you’re feeling in the first place. Don’t write about the beauty of the sun sinking under the horizon, or the tranquil glow of freshly fallen snow on the pavement; write about the visceral responses these visual cues trigger in you. Write about art and death, about feminism and patriarchy and racial inequality. Writing this way forces the mind to engage with a concept, to thread a coherent narrative line in order to make sense of it, render it less obscure, understand it. And there are plenty of things I don’t know.