function [L] = logl_dur(b)
% The following is the loglikelihood function for a duration model with an
% exponential distribution.

global x1 x2 T t

b1 = b(1);
b2 = b(2);

XB = (x1*b1 + x2*b2);

L = 0;

for i = 1:T
  L = L + XB(i) - t(i)*exp(XB(i));   
end

L = -L;

end

