Answer: 40 points
Step-by-step explanation:
Step 1: Since you every incorrect guess costs you the points you wagered,and a set confidence level of "I think I know it" i worth *80 points, you will lose this 80 points after an incorrect guess.
Step 2: Since if I guess right on the second chance, I earn half of the points I lost, I will earn back 80/2 points = 40 points