public ResidentialSite(Zone zone)
 {
     this.zone = zone;
 }
 public ResidentialSite CreateResidentialSite()
 {
     var zone = new Zone("B", 0.07, 0.06, new DateTime(1997, 6, 5), new DateTime(1997, 8, 31));
     return new ResidentialSite(zone);
 }
 public DisabilitySite CreateDisabilitySite()
 {
     var zone = new Zone("A", 0.06, 0.07, new DateTime(1997, 5, 15), new DateTime(1997, 9, 10));
     return new DisabilitySite(zone);
 }
 public DisabilitySite(Zone zone)
 {
     this.zone=zone;
 }