Pass/Fail Deg Requirement and graduate over the summer?

[academicinprogress]

Hi,

I'm an undergrad at a public university, and I'm set to graduate in May 2020. I'm an Econ and Math major, and a Stats minor. My current Econ GPA is 3.97, Math is 3.65, and Stats is 3.9. I've taken all the classes required for the Econ major and Stats minor, and I'm currently in the last 2 classes I need to complete my Math major. However, one of those 2 classes is extremely hard, and way out of my league, and I don't see myself getting better than a C+/B- in it. I'm really scared it will sink my Math GPA, and I am considering Pass/Failing the class (meaning the grade I get will not count towards my GPA or my major). If I do that, I can either graduate this May with a Math minor, or take another Math class over the summer to graduate with the Math major. 

I'm not sure what the best decision will be. I'm hoping to apply to graduate school for Economics in Fall 2020, and I don't know what will reflect more poorly on me: a poor grade in this Math class, or the fact that it took me an extra summer class to finish my degree. Any advice would be very appreciated!