For the car on a level air track, a student has a video clip that shows the car at positions x$1=0\mathrm{.}580$ m and x$2=0\mathrm{.}772$ m in adjacent frames. The video clip was recorded at a frame rate of $15$ frames$/$second$.$ Find the average speed of the car in m$/$s$.$ Enter the number only, not the unit. Correct Answer: $2\mathrm{.}880$ How did they get this answer? Please explain fully.