Qwizy BINGO - Related Rates Question #30

$Solve each related rate problem. An observer stands $600\,ft$ away from a launch pad to observe a rocket launch. The rocket blasts off and maintains a velocity of $400\,ft/sec.$ Assume the scenario can be modeled as a right triangle. How fast is the observer to rocket distance changing when the rocket is $800\,ft$ from the ground?$