$2-$ Use the database shown in Figures $4$&$5$ to answer the following questions.

ROBCOR is an aircraft charter company that supplies on$-$demand charter flight services using a

fleet of four aircraft. Aircrafts are identified by a unique registration number. Therefore, the aircraft

registration number is an appropriate primary key for the AIRCRAFT table.

Table name: CHARTER

Database name: Ch$03\_$AviaCo

The destinations are indicated by standard three$-$letter airport codes. For example,

STL $=$ St$.$ Louis, MO

ATL $=$ Atlanta, GA

BNA $=$ Nashville, $TN$

Table name: AIRCRAFT

$A{C}_T$TAF $=$ Aircraft total time, airframe $(hours)$

$A{C}_T$TEL $=$ Total time, left engine $(hours)$

$A{C}_T$TER $=$ Total time, right engine $(hours)$

In a fully developed database system, such attribute values would be updated

by application software when the CHARTER table entries are posted.

Table name: MODEL

Customers are charged per roundtrip mile, using the MOD$\_$CHG$\_$MILE rate. The MOD$\_$SEATS gives the total number of seats in the

airplane, including the pilot and copilot seats. Therefore, a PA$31-350$ trip that is flown by a pilot and a copilot has eight passenger seats

available. a$)$ For each table, identify the primary key and foreign key$($s$)$ when possible.

b$)$ Identify all the relationships between the tables.

You want to see data on charters flown by either Robert Williams $($employee number$105)$ or John

Lange $($employee number $104)$ as pilot or copilot, but not charters flown by both of them. Complete

Problems $2-$c to $2-$e to find this information.

c$)$ Create the table that would result from applying the SELECT and PROJECT relational

operators to the CHARTER table to return only the CHAR$\_$TRIP, CHAR$\_$PILOT, and

CHAR$\_$COPILOT attributes for charters flown by either employee $105$ or employee $104$

as pilot or copilot.

d$)$ Create the table that would result from applying the SELECT and PROJECT relational

operators to the CHARTER table to return only the CHAR$\_$TRIP, CHAR$\_$PILOT, and

CHAR$\_$COPILOT attributes for charters flown by both employee $105$ and employee $104.$

e$)$ Create the table that would result from applying a DIFFERENCE relational operator of

your result from Problem $2-$c to your result from Problem $2-$d$.$