What is managerial accounting?

What is managerial accounting?

1. What are the diverse users for managerial accounting information?  
2. How does managerial accounting information assist managers in performing the roles of planning, directing, and controlling? what would be an example for each of the performing roles?
3. What are the two factors that must be considered when deciding on an accounting system?
4. Some financial mangers prefer capital budgeting models such as internal
5. rate of return (IRR) or non- discounted payback models over the net present value (NPV) the model, which is preferred by academic financial analysts. Why? Briefly discuss. （more words as more as possible).