Symmetric Random Walk Displacement via CLT

A particle performs a symmetric random walk: at each step $i$, it moves $X_i = +1$ or $X_i = -1$, each with probability $1/2$, independently. After $n = 400$ steps, the position is $S_{400} = \sum_{i=1}^{400} X_i$.

(a) What does the LLN say about $S_n / n$ as $n \to \infty$?

(b) Using the CLT, approximate $P(S_{400} > 10)$.

You may use $\Phi(0.50) \approx 0.6915$.