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+\documentclass[compose]{exam-n}
+\begin{document}
+
+\begin{question}{30} \comment{by Andrew Davies}
+
+The Friedmann equations are written, in a standard notation,
+\begin{gather*}
+H^2 = \frac{8\pi G\rho}{3}-\frac{kc^2}{R^2}+\frac{\Lambda}{3},\\
+\Diffl {}t (\rho c^2R^3)=-p\Diffl {R^3}t,
+\end{gather*}
+Discuss briefly the meaning of each of  $H$, $\rho$ , $k$ and
+$\Lambda$. \partmarks{4}
+
+Suppose the Universe consists of a single substance with equation
+of state  $p=w\rho c^2$, where  $ w=$constant.  Consider the
+following cases, with $k=\Lambda=0$:
+
+\part For $w = 0$, find the relation between $R$ and $\rho$.  Hence
+show that $H=\frac{2}{3t}$. What is the physical interpretation of
+this case?
+\partmarks{8}
+
+\part In the case $w=-1$ , show that  $H = $constant and $R = A \exp(Ht)$,
+with $A$ constant.
+\partmarks{4}
+
+\part Explain how the case, $w=-1$, $k=\Lambda=0$, $\rho=0$ is
+equivalent to an empty, flat, Universe with a non-zero $\Lambda$.
+\partmarks{2}
+
+\part Consider a model Universe which contained matter with equation
+of state with $w = 0$ for $0 < t < t_0$, but which changes to
+$W=0$ for $t\ge t_0$ without any discontinuity in $H(t)$.
+Regarding this second stage as driven by a non-zero $\Lambda$ what
+is the value of $\Lambda$ if $t_0 = 10^{24}$\units{\mu s}? Define the
+dimensionless deceleration parameter, $q$, and find its value
+before and after $t_0$.
+\shout{Shout it loud: I'm a geek and I'm proud}
+\partmarks{8}
+
+Note: that's
+\[
+t_0=10^{24}\units{\mu s}\qquad\text{with a letter mu: $\mu$}.
+\]
+
+\part To what extent does this idealized model resemble the currently
+accepted picture of the development of our Universe?
+\partmarks{4}
+\end{question}
+\end{document}