Microeconomics) total & marginal utilities

1.At which rate is total utility increasing: a constant rate, a decreasing rate, or an increasing rate? How do you know?
2.A rational consumer will purchase only 1 unit of the product represented by these data, since that amount maximizes marginal utility.Do you agree? Explain why or why not.
3.It is possible that a rational consumer will not purchase any units of the product represented by these data.Do you agree? Explain why or why not.