Solution
= Solution
If $\xi_1\le C$, then $t<T_{N_t+1}\le t+C$. Taking expectations and using (b) yields $\lambda t-1<E N_t\le\lambda(t+C)-1$. Divide by $t$.
= Solution
If $\xi_1\le C$, then $t<T_{N_t+1}\le t+C$. Taking expectations and using (b) yields $\lambda t-1<E N_t\le\lambda(t+C)-1$. Divide by $t$.