A stratified random sample is designed with two strata: $N_1 = 800$ and $N_2 = 200$. We aim to estimate the population mean with a total sample $n = 100$. If stratum standard deviations are $S_1 = 5$ and $S_2 = 15$, what are the optimal sample sizes $n_1$ and $n_2$ under Neyman allocation?