MathML example

The following (semantically bogus) example may not display correctly in Firefox 3.6 (or earlier versions and other browsers), but should in Firefox 4:

$$\left\{a\sqrt[9]{k·{\ell \mp \left(2c\right)}^z\frac{\frac{c\pm 1}{n}}{{(t}^{-1}2b)}-\Delta 8y}\because \exists a\le n\right\}\not\simeq \frac{n}{{{\rm P}}_e^{\ell }}\lfloor \partial t-\phi \rfloor$$

For those who cannot see it, here's an image of what it should look like: