PROGRAM BT1_11
	REAL LAMDA
	PARAMETER (NMAX=12,LAMDA=137.0/100.0)
	DIMENSION PK(0:NMAX)
	INTEGER N,K
	N=4
	DO K=0,N
	   PK(K)=POSSION(LAMDA,K)
	ENDDO
	WRITE(*,'(" TRUNG BINH MOT NAM CO ",F4.2," NGAY CO MUA DA")')LAMDA
	WRITE(*,*)' XAC SUAT TRONG MOT NAM CO: '
	DO K=0,N
	   WRITE(*,'(I3," NGAY CO MUA DA= ",F8.4)')K,PK(K)
	ENDDO
	END

	  
	FUNCTION POSSION(LAMDA,K)
	REAL LAMDA
! HAM NAY TINH XAC SUAT SU KIEN XUAT HIEN K LAN THEO POSSION
	POSSION=EXP(-LAMDA)*LAMDA**K/FAC(K)
	RETURN
	END

	FUNCTION FAC(N)
! TINH N! (N GIAI THUA)
	REAL TMP
	  IF (N.LT.0) THEN
	     WRITE(*,*)' INVALID NUMERIC INPUT IN FAC FUNCTION'
		 STOP
	  ELSE IF (N.EQ.0.OR.N.EQ.1) THEN
	     FAC=1.0
		 RETURN
	  ELSE
	     TMP=1.0
		 DO I=2,N
	        TMP=TMP*REAL(I)
		 ENDDO
		 FAC=TMP
		 RETURN
	ENDIF
	END