SUBROUTINE LUBKSB(A,N,NP,INDX,B)  
C  
C CHANGE RECORD  
C  
      DIMENSION A(NP,NP),B(N),INDX(N)  
C  
      II=0  
      DO 12 I=1,N  
        LL=INDX(I)  
        SUM=B(LL)  
        B(LL)=B(I)  
        IF(II.NE.0)THEN  
          DO 11 J=II,I-1  
            SUM=SUM-A(I,J)*B(J)  
   11     CONTINUE  
        ELSE IF(SUM.NE.0.)THEN  
          II=I  
        ENDIF  
        B(I)=SUM  
   12 CONTINUE  
      DO 14 I=N,1,-1  
        SUM=B(I)  
        IF(I.LT.N)THEN  
          DO 13 J=I+1,N  
            SUM=SUM-A(I,J)*B(J)  
   13     CONTINUE  
        ENDIF  
        B(I)=SUM/A(I,I)  
   14 CONTINUE  
      RETURN  
      END