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)} 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 }