Please help :( im stuck!! Explain please:
A building in the shape of a rectangular pyramid is used to store construction stones. The building has a volume of 21,000 ft^3 . A new building is being designed. It will also be in the shape of a rectangular pyramid, but compared to the existing building, the length of its base will be scaled by a factor of 2/3 , and the width of its base will be scaled by a factor of 5/3 . The height of the new building will be scaled such that the volume of the new building will be the same as the existing building. What scale factor will be used for the height of the new building?