of course not
Certainly not. The phrase implies that a negative response should be obvious. A: "Would you mind picking me up from the airport?" B: "Of course not! What time do you land?" A: "Are you going to sign up for this overtime refund scheme?" B: "No, of course not, it's a total ripoff!"
of ˈcourse not
(also ˈcourse not informal) used to emphasize the fact that you are saying ‘no’: ‘Are you going?’ ‘Of course not.’‘Do you mind?’ ‘No, of course not.’