Howdy, partner! So, your GPA and GRE aren't bad, but they're not STELLAR, either. What helps you out here is your ECs, which are SOLID, dude, especially the Math prize and the internships, which show your numbers experience/talent and use of your skills outside the classroom. All that said, this is an issue of timing. If you are going to have a chance at Columbia, or any other big program, you've got to apply Fall. ED for the MBA program, for sure. It shows your seriousness about the program, and the spring just... well, there aren't as many slots, and the adcoms have been looking at apps for MONTHS, so you've got a better chance of getting lost in the shuffle. I hope this helps, my friend, and please reach out if you need any more input!