You are trying to determine the height of a building whose base is on a level plan on which you stand. You are at the base of a vertical pole that you are able to climb. From the base of the pole, you measure the angle to the top of the building to be 30. You climb a certain distance up the pole and measure again: the angle is now 28. After climbing 10 feet further up the pole, you measure once more, and find the angle is 27. How tall is the building?