Sponsored ads use an auction-based cost-per-click (CPC) inventory-buying mode. The winner of the auction has to pay an amount slightly higher than the second highest CPC bid if their ad is clicked. So, in order to win the auction, Manuel has to pay an amount slightly higher than the second highest bid ($0.78) which is around $0.79.
This question is a part of the Amazon Sponsored Ads Foundations Certification Assessment. You can find answers to all the questions asked in this exam in our Amazon Sponsored Ads Foundations Certification Assessment Answers page.