If the distance between planes , $\;4x - 2y -4z+1=0\;$ and $\;4x - 2y -4z+d=0\;$ is 7 , then d is :

Question

$(a)\;41\;or\;-42 \qquad(b)\;42\;or\;-43\qquad(c)\;-41\;or\;43\qquad(d)\;-42\;or\;44$