Which situation would use the midpoint formula?

a-Calculate the distance from Trenton to Jackson using a map.
b-Find the slope between two points.
c-Two friends live across town from each other. A park located in the center of town is the same distance from each friend. Find the location of the park when given the location of the each friend's house.
d-Locate the ordered pair (5,-2) on a coordinate plane.

(can chose more than one)