= Solution
Use the preparation and measurement from part (i). `RandomReset` returns the <density matrix> $\rho_R=(|0\rangle\langle0|+|1\rangle\langle1|)/2=I/2$, a <maximally mixed state>. In the $|+\rangle,|-\rangle$ basis its two outcomes each have <probability> $1/2$. In contrast, `RandomFlip` always gives outcome 0.
Guess `RandomFlip` after 0 and `RandomReset` after 1. With the supplied equal priors,
$$
\boxed{P_{\rm success}=\frac12\Pr(0\mid\texttt{RandomFlip})+\frac12\Pr(1\mid\texttt{RandomReset})=\frac12+\frac14=\frac34.}
$$
An outcome 1 identifies the reset action, but outcome 0 does not identify the flip action with certainty. For example, <Bayes' theorem> gives posterior <probability> $2/3$ for the flip action after 0. The total success rate already accounts for the reset runs that also produce 0.
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