Solve state matrix using Runge-Kutta 4th Order

I have this state space equation in the form of (dx = Ax+ Bu)

a(i,j) is constants

[dx1; dx2; dx3] = [a11 a12 0 0; 0 a22 a23 0; a31 0 a33] * [x1; x2; x3] + [b1; 0; 0]*u

where u is step signal

time step (h)= 0.01

run upto 30sec

how can i solve this equation using runge kutta 4th order? can anyone help in detail by code