A student investigates the average contact force exerted on a cart during a collision with a fixed sensor. In each trial, a cart of total mass \(m\) travels along a horizontal track with an initial speed \(v_i\) in the positive direction, strikes the sensor, and rebounds with a speed \(v_f\) in the negative direction. The collision lasts for a measured time interval \(\Delta t\). Which of the following graphs will yield a best-fit line with a slope equal to the magnitude of the average force \(\bar{F}_{\text{avg}}\) exerted by the sensor on the cart?