% FIGURE 5.8.1
      function FUNB = FUNB581(X,K,I)
      global TKP1
%                              INTEGRAND FOR (K,I)-TH ELEMENT           
%                              OF "B" MATRIX                       
      PK  = PHI(K,0,X);
      PI  = PHI(I,0,X);
      FUNB = exp(0.5*X^2*TKP1)*PK*PI;
