C	TWCOM2
C	T=X-DT<6 CONST>
C	OR
C	T=X <5 CONST>
C	CP=KA*D/VP<(K21-ALFA)/[(KA-ALFA)*BETA-ALFA)]*EXP(-ALFA*T)
C		+(K21-BETA)/[KA-BETA)*(ALFA-BETA)]*EXP(-BETA*T)
C		+(K21-KA)/[(ALFA-KA)*(BETA-KA)]*EXP(-KA*T)>
C
C
C	INITIAL VALUES MUST BE SUPPLIED FOR
C	KA	K21	ALFA	BETA	D/VP	DT	 (IN THAT ORDER)
C
C
C	FUNCTION IS VERY DIFFICULT TO ITERATE VERY GOOD DATA
C	IS REQUIRED
C
C	ERRORS ARE 1)IF ANY DIVISOR=0
C		2)IF THE EXPONENTS >85
C
	FUNCTION FUNCT(ARG,X,Y)
	DIMENSION ARG(1)
	COMMON IFEL
	FKA=ARG(1)
	FK21=ARG(2)
	ALFA=ARG(3)
	BETA=ARG(4)
	DOSV=ARG(5)
	T=X-ARG(6)
	E1=ALFA*T
	IF(I1.GT.100.OR.E1.LE.0)IFEL=1
10	E2=BETA*T
	IF(E2.GT.100.OR.E2.LE.0)IFEL=2
20	E3=FKA*T
	IF(E3.GT.100.OR.E3.LE.0)IFEL=3
31	D1=(BETA-ALFA)*(FKA-ALFA)
	IF(D1.EQ.0)GOTO 4
40	D2=(FKA-BETA)*(ALFA-BETA)
	IF(D2.EQ.0)GOTO 5
50	D3=(ALFA-FKA)*(BETA-FKA)
	IF(D3.EQ.0)GOTO 6
60	FUNCT=(FK21-ALFA)/D1*EXP(-E1)+(FK21-BETA)/D2*EXP(-E2)
     1+(FK21-FKA)/D3*EXP(-E3)
	FUNCT=FUNCT*DOSV*FKA
	FUNCT=Y-FUNCT
100	RETURN
6	IFEL=1
5	IFEL=1+IFEL
4	IFEL=IFEL+4
	RETURN
	END