ECON 110/6.0 (Queen’s main campus) or ECON 111/3.0 and ECON 112/3.0 (if studying at the Bader International Study Centre) (Economics: see What ECON course should I take?)
MATH 126/6.0 or MATH 121/6.0 (calculus: see What MATH course should I take?)
For a list of electives see here