Business writing is a specific type of assignment. It should be composed according to the plan. It is important to pay attention to the details. The size also matters here. This type of writing can't be too long. It is not a complicated kind of paper if you are confident about its content. In case if you have some doubts during the process of Writing a Business Memo you can find an example here https://writology.com/writing-business-memo. Following the example might make things a bit easier.