A gun fires "Bang!" at location A, and it hits a target "Whack!" at location B a distance 'd' away from location A. Where must an observer stand to

A gun fires "Bang!" at location A, and it hits a target "Whack!" at location B a distance 'd' away from location A. Where must an observer stand to hear "Bang!" and "Whack!" at the same time? The bullet travels at speed 'v' and the speed of sound is 's' where 's' is greater than 'v'. Show your work.

Hint: think conic sections.