Final answer:
The floor of Class B airspace at Dallas Executive Airport cannot be determined without the specific sectional chart. Pilots use these charts to identify airspace boundaries, which are depicted with limits in hundreds of feet MSL.
Step-by-step explanation:
The question pertains to the airspace classifications and boundaries at Dallas Executive Airport (RBD), which falls under the subject of Geography, with particular relevance to aviation geography and air traffic control. The student is asked to determine the floor of Class B airspace for the specified area. Unfortunately, without Figure 25 or the actual sectional chart, we cannot provide the specific floor of the Class B airspace at Dallas Executive. Normally, when reading a sectional chart, the floor of the Class B airspace is indicated in hundreds of feet MSL (Mean Sea Level) on the chart. The numbers provided are usually the upper limit and the lower limit of the Class B airspace, and pilots need to be familiar with reading these sectional charts to navigate the airspace safely. For instance, it could be depicted on the sectional chart as '30/12', which would mean the Class B airspace extends from 3,000 feet MSL to 12,000 feet MSL.
In this case, the correct figure and airspace information is necessary to determine the exact floor of the Class B airspace. Pilots rely on up-to-date sectional charts and other resources such as the FAA's publications or their websites to obtain current airspace information.