approximation using floating point arithmetic

Question

Let $x=2.14366$ and $y=2.14363$ and $d=x-y.$ If $d*$ is the value of d computed using $5-$digit decimal floating point arithmetic, find the relative error.

For this question I know how to calculate the relative error, but the example gives $d^*$ as being $d^* = o.ooo1$ am unsure how this is calculated?.

Answer 1

You have only five digits of accuracy in this computation, so $x$ rounds to $x^* = 2.1437$ and $y$ rounds to $y^* = 2.1436$.

Now compute $x^* - y^*.$