Displacement vectors of 4 km north, 2 km south, 5 km north, and 5 km south combine to a total displacement of

south = -(north)

Displacement = (4 km north) + (2 km south) + (5 km north) + (5 km south)

Displacement = (4 km north) - (2 km north) + (5 km north) - (5 km north)

Displacement = (4 - 2 + 5 - 5) km north

Displacement = 2 km north

f=ma newton's second law 7x8=56n