Amelia needs to estimate the quantity , where , , and are large positive integers. She rounds each of the integers so that the calculation will be easier to do mentally. In which of these situations will her answer necessarily be less than the exact value of ?
She rounds down, and she rounds and up.
She rounds and down, and she rounds up.
She rounds and down, and she rounds up.
She rounds up, and she rounds and down.
She rounds all three numbers up.
