In a tug-of-war game on one campus, 15 students pull on a rope at both ends in an effort to displace the central knot to one side or the other. Two students pull with force 192 N each to the right, four students pull with force 92 N each to the left, five students pull with force 68 N each to the left, three students pull with force 152 N each to the right, and one student pulls with force 260 N to the left. Assuming the positive direction to the right, express the net pull on the knot (in N) in terms of the unit vector î.