For the following database:

PEAK (NAME, ELEVATION, DIFFICULTY, MAP, REGION)

CLIMBER (NAME, SEX)

PARTICIPATED (TRIP_ID, NAME)

CLIMBED (TRIP_ID, PEAK, WHEN_CLIMBED)

PEAK gives info about the mountain peaks that the user is interested in. The table lists the name of each peak, it elevation(in ft), its difficulty level(on a scale of 1-5), the map that it is located on, and the region of the Sierra Nevada that it is located in.

CLIMBER lists the members of club, and gives their name and gender.

PARTICIPATED gives the set of climbers who participated in each of the various climbing trips. The number of participants in each trip varies.

CLIMBED tells which peaks were climbed on each climbing trip, along w/ the data that each peak was climbed.

Provide the extended relational algebra expression tree which answers the following questions:

Who has climbed a peak rated class 5 in difficulty?

Which peaks have been climbed exactly once?