Let $X_1, X_2, \dots, X_{100}$ be i.i.d. standard normal random variables. Let $Y_i = I(X_i > 0.84)$, where $I$ is the indicator function, and note that the standard normal CDF satisfies $\Phi(0.84) \approx 0.80$. Let $S = \sum_{i=1}^{100} Y_i$. Using the normal approximation with a continuity correction, find the approximate value of $P(S \le 15)$ expressed in terms of the standard normal CDF $\Phi$.