Height of a Hot-Air Balloon. As a hot-air balloon began to rise, the ground crew drove $1.2 \mathrm{mi}$ to an observation station. The initial observation from the station estimated the angle between the ground and the line of sight to the balloon to be $30^{\circ} .$ Approximately how high was the balloon at that point? (We are assuming that the wind velocity was low and that the balloon rose vertically for the first few minutes.)