Pricing a digital call

Under Black-Scholes, a cash-or-nothing digital call pays $1 at time $T$ if $S_T > K$ and nothing otherwise. Find its price. Evaluate it for $S_0 = K = 100$, $\sigma = 20\%$, $T = 1$, $r = 5\%$, and explain how to get the same number from vanilla call prices.