7. Why is Crank-Nicolson's scheme called an implicit scheme? Using Crank-
Nicolson's implicit method, solve $$16\frac{\partial u}{\partial t} = \frac{\partial^2 u}{\partial x^2}$$, $$0<x<1, t>0$$, given that
$$u(x, 0) = 0, u(0, t) = 0, u(1, t) = 100t$$, compute u for a one-time
step.