(1 point) Let = (3a²x + 6ay²) + (6z³ - 2ay) - (z+6x² + 6y²)k. (a) Find the value(s) of a making div = 0 a = (1,2/3) (Enter your value, or if you have more than one, enter a comma-separated list of your values.) (b) Find the value(s) of a making div a minimum a = 0 (Enter your value, or if you have more than one, enter a comma-separated list of your values.)