Literally the first thing you read on their website is “Upon graduating, students find opportunities in the private and public sectors, from financial services to software development”. http://www.mccormick.northwestern.edu/applied-math/undergraduate/index.html
Also this: “Students who earn a bachelor of science in applied mathematics are well prepared to function as professional mathematicians, excel in graduate study, work to advance the field, or apply their knowledge in other areas that might include finance, business management, law, or medicine.” from the link to their undergrad program http://www.mccormick.northwestern.edu/applied-math/undergraduate/bachelor-of-science/index.html
It seems like the major would then make you competitive for finance/business jobs.
As for the co-op, I’d suggest emailing the people that run the program at NU and finding out that way. You’d get a more correct and direct answer than by asking us. Here’s a link to the co-op page; email links are in the right-hand column: http://www.mccormick.northwestern.edu/career-development/programs/co-op/