T-SQL Insert Delete Update function

-- ============================================= 
-- Write an insert, delete and update trigger named 
-- trgCharterUpdate for the Charter Table. These will 
-- update the Price column on the Charter table and 
-- the Number of Trips, Distance Flown, Hours Flown, 
-- Fuel and Oil Used on the Aircraft table. Be aware 
-- that a charter can change the aircraft which will 
-- affect two aircrafts--there will be a trigger fired for each.
-- ============================================= 
CREATE TRIGGER trgCharterUpdate
ON CHARTER
AFTER INSERT, UPDATE, DELETE
NOT FOR REPLICATION
AS 
IF @@ROWCOUNT > 0
    BEGIN
    DECLARE @ActionType int
       , @RowCount int
       , @AC_NUMBER nvarchar(50)
       , @FuelCharge money = 0.79 -- VARIABLE PER GALLON FUEL RATE
       , @WaitCharge money = 112.50 ; -- VARIABLE PER HOUR WAIT RATE

       SET @ActionType = 0 ;

       SELECT @RowCount = count(*)
       FROM deleted ;

       IF @RowCount>0
         SET @ActionType = 1 ;

       SELECT @RowCount = count(*)
       FROM inserted ;

       IF @RowCount > 0
         SET @ActionType = @ActionType + 2 ;

       IF @ActionType = 1
         SELECT @AC_NUMBER = AC_NUMBER
         FROM deleted ;
       ELSE
         SELECT @AC_NUMBER + AC_NUMBER
         FROM inserted ;

       UPDATE CHARTER
         SET C.PRICE = foo1.Price
       FROM (
         SELECT CAST(ROUND(SUM (([MOD_CHG_MILE]*[CHAR_DISTANCE]) + ([CHAR_FUEL_GALLONS]* @FuelCharge) + ([CHAR_HOURS_WAIT]* @WaitCharge)),2) AS decimal(6,2)) AS Price
         FROM CHARTER C
         GROUP BY C.CHAR_TRIP, C.AC_NUMBER
         )
         AS foo1
       UPDATE AIRCRAFT
       SET   TripCount = foo.Trips
         , DistanceFlown = foo.Distance
         , HoursFlown = foo.Hours
         , FuelUsed = foo.Fuel
         , OilUsed = foo.Oil
       FROM AIRCRAFT A 
         INNER JOIN 
         (
          SELECT AC_NUMBER
              , Count(C.CHAR_TRIP) AS Trips
              , Sum(C.CHAR_DISTANCE) AS Distance
              , Sum(C.CHAR_HOURS_FLOWN) AS Hours
              , Sum(C.CHAR_FUEL_GALLONS)  AS Fuel
              , Sum(C.CHAR_OIL_QTS) As Oil
          FROM CHARTER C
          GROUP BY AC_NUMBER
         ) 
         AS foo
       ON A.AC_NUMBER = foo.AC_NUMBER

       CASE @ActionType
         WHEN 1 THEN 'Delete'
         WHEN 2 THEN 'Insert'
         WHEN 3 THEN 'Update'
END