ined below, the values of U, T and A may need to be adjusted in order for the congruence equations to have a solution. When a <i>zh&#257;ng</i> cycle is pre-specified, only U and A can be adjusted. Whereas in the second method U, T and A can be adjusted freely. This is the difference between the two methods in the computation of the superior epoch.</p><br><subsect id="conditions">Conditions for the Existence of a Solution</subsect><p>As mentioned above, it is not guaranteed that the system of congruence equ