The ____ utility is used to determine if a specific machine located at a specific IP address is online.?

MIME is a protocol that's used when you're

a. sending a video file to YouTube. b. encrypting an e-mail message. c. executing a CGI script. d. sending an e-mail that has a photo attached.

Describe the relations that would be produced by the following tuple relational calculus expressions:

(a) {H.hotelName | Hotel(H) ? H.city = ‘London’} (b) {H.hotelName | Hotel(H) ? (?R) (Room(R) ? H.hotelNo ? R.hotelNo?? R.price ?50)} (c) {H.hotelName | Hotel(H) ? (?B) (?G) (Booking(B) ? Guest(G) ? H.hotelNo ? B.hotelNo?? B.guestNo = G.guestNo ?? G.guestName = ‘John Smith’)} (d) {H.hotelName, G.guestName, B1.dateFrom, B2.dateFrom | Hotel(H) ? Guest(G) ? Booking(B1) ? Booking(B2) ? H.hotelNo ? B1.hotelNo?? G.guestNo = B1.guestNo ?? B2.hotelNo = B1.hotelNo ? B2.guestNo = B1.guestNo ?? B2.dateFrom ? B1.dateFrom}