= Solution
Suppose for contradiction that $\|\widehat\theta(Z_{\gamma,\tau})\|_2\leq M$ uniformly in $\gamma,\tau$. Choose $\gamma>M+1$, so part d applies to every fitted value and gives $L(\widehat\theta)\geq\rho(\tau)$. For this fixed $\gamma$, part c gives the competing bound
$$
L(\theta_\gamma)
\leq h\rho\!\left(M_y+\gamma\max_i|x_{i1}|\right)+\lambda\gamma,
$$
which is independent of $\tau$. Since $\rho(\tau)\to\infty$, choose $\tau$ so that the lower bound exceeds this upper bound, contradicting optimality. Thus $n-h+1$ replacements can make the estimate unbounded, and
$$
\epsilon^*(Z,\widehat\theta)\leq\frac{n-h}{n}.
$$
Together with part b, the <replacement breakdown point> is exactly $(n-h)/n$.
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