Rising Balloon. A hot-air balloon rises straight up from the ground at a rate of 120 ft /...

Rising Balloon. A hot-air balloon rises straight up from the ground at a rate of 120 ft / min. The balloon is tracked from a rangefinder on the ground at point P, which is 400 ft from the release point Q of the basket. Let d = the distance from the balloon to the range-finder and t = the time, in minutes, since the balloon was released. Express d as a function of t.