Fireworks Display Suppose that two people standing 2 miles apart both see the burst from a fireworks display. After a period of time, the first person standing at point A hears the burst. One second later, the second person standing at point B hears the burst. If the person at point B is due west of the

person at point A and if the display is known to occur due north of the person at point A, where did the fireworks

display occur?

I tried using an ellipse, but I did not get anywhere. If the speed of sound is v=1129ft/s and the lightning is due north of A, then can't I use the fact that the sum of the distances from the foci is a constant? What am I doing wrong?