Following is a demo of the extra credit program.
Welcome to SWI-Prolog (threaded, 64 bits, version 7.6.4) SWI-Prolog comes with ABSOLUTELY NO WARRANTY. This is free software. Please run ?- license. for legal details. For online help and background, visit http://www.swi-prolog.org For built-in help, use ?- help(Topic). or ?- apropos(Word). ?- solve. abigail's birthday is in february on a monday. brenda's birthday is in december on a wednesday. mary's birthday is in june on a sunday. paula's birthday is in march on a friday. tara's birthday is in july on a saturday. true .