premise: An administrator must assign parking spaces to six new employees: Robertson, Souza, Togowa, Vaughn, Xu, and Young. Each of the six employees must be assigned one of the following parking spaces: #1, #2, #3, #4, #5, or #6. No two employees can be assigned the same parking space. The following rules govern the assignment of parking spaces: Young must be assigned a higher-numbered parking space than Togowa. Xu must be assigned a higher-numbered parking space than Souza. Robertson must be assigned a higher-numbered parking space than Young. Robertson must be assigned parking space #1, #2, #3, or #4. For how many of the six new employees is the assignment of a parking space limited to one of only two possible spaces?
hypothesis: four