6. For the system of equations it dy it = -3e3xty + y, (a) (5 points) show that the system is a Hamiltonian system and find its Hamiltonian function H(x, y); (b) (5 points) show that the Hamiltonian function H is a conserved quantity, i.e. for any solution (x(t), y(t)), H(x(t), y(t)) is identically a constant