Answer the following with relational algebra.

a. List the flight number, departure airport code, scheduled departure time, arrival airport code, scheduled arrival time, and weekdays of all flights or flight legs that depart from some airport in the city of Houston and arrive at some airport in the city of Los Angeles.

b. List all fare information for flight number co197.

c. Retrieve the number of available seats for flight number co197 on 2009-10-09.

AIRPORT \begin{tabular}{|l|l|l|l|} \hline Aiport_code & Name & City & State \\ \hline \end{tabular} FLIGHT \begin{tabular}{|l|l|l|} \hline Fight_number & Airline & Weekdays \\ \hline \end{tabular} FLIGHT_LEG \begin{tabular}{|c|c|c|c|} \hline Flight_number & Leg_number & Departure_airport_code & Scheduled_departure_time \\ \hline Arrwal_airport_code & Scheduled_artival_time \\ \hline \end{tabular} LEG_INSTANCE \begin{tabular}{|c|c|c|c|c|c|c|} \hline Flight_number & Leg_number & Date & \multicolumn{2}{|c|}{ Number_of_available_seats } & \multicolumn{2}{c|}{ Aiplane_id } \\ \hline \hline Departure_airport_code & Departure_time & Arrwal_airport_code & Arrival_time \\ \hline \end{tabular} FARE \begin{tabular}{|l|l|l|l|} \hline Fight_number & Fare_code & Amount & Restrictions \\ \hline \end{tabular} AIRPLANE_TYPE \begin{tabular}{|l|l|l|} \hline Aiplane_type_name & Max_seats & Company \\ \hline \end{tabular} CAN_LAND \begin{tabular}{|l|l|} \hline Aiplane_type_name & Airport_code \\ \hline \end{tabular} AIRPLANE \begin{tabular}{|l|l|l|} \hline Aiplane_id & Total_number_of_seats & Aiplane_type \\ \hline \end{tabular} SEAT_RESERVATION \begin{tabular}{|l|l|l|l|l|l|} \hline Flight_number & Leg_number & Date & Seat_number & Customer_name & Customer_phone \\ \hline \end{tabular}