In the book, it says that actual investment spending will be greater than planned investment spending when there is an unplanned increase in inventories, so I am little confused. I think this question is the same as that in the book. How can I judge these two?

If people's MPS is high, and the government cuts the tax rate, what will happen to the aggregate demand and consumption?
I think since people have more disposable income, they will increase consumption although they will save more increased money, so the consumption and aggregate demand will increase. What's wrong about my opinion?