a) Solve the following system of equations using the Crank-Nicolson method ordinary differentials, for the first two steps in t using At = 0.1 du, dt =12u +4u + 6te ; u(0)=1 du, du -3- =6u, +9u; u (0)=-1 dt dt 2- b) Determines the order of the local error associated with a method that leads to the following one-step formula +1= 12-62h+2h 12+62h+2h by discretizing the following ordinary differential equation: du =-Au, u(0)=uo. dt Check your result by applying the method to the case where = 0.5, u, = 100 and h = 11 40'80