The height of an (axially symmetric) pipe z as a function of the distance from the

axis of symmetry is $\displaystyle z = 2 - 2x^{2} $ , where both z and x are measured in metres, and where $\displaystyle 0 \leq z \leq 2 $ and $\displaystyle 0 \leq x \leq 1 $ . What is the total volume of hay in cubic metres

in the haystack?

This question makes no sense to me,How does 'haystack' come into this, surely it talking about a pipe?

Any help appreciated.