Knowing that the generators Pβ of translations and the components Qα of the position operator
Q satisfy the commutation relation [Qα,Pβ]=iℏδαβI, show that the operator J=Q×P (the
generator of rotations) satisfies the following commutation relations:
a) [Jα,Jβ]=iℏεlonαβγJγ
b) [Jα,Pβ]=iℏεlonαβγPγ