$2-$ 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

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

AC$\_$TTAF $=$ Aircraft total time, airfame $($hours$)$

AC$\_$TTEL $=$ Total time, left engine $($hours$)$

$A{C}_{-}$TTER $=$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.