  The ambition constrained validity and the model witness problems in the logic
UCL, for reasoning about circuits with unreliable gates, are analyzed.
Moreover, two additional problems, motivated by the applications, are studied.
One consists of finding bounds on the reliability rate of the gates that ensure
that a given circuit has an intended success rate. The other consists of
finding a reliability rate of the gates that maximizes the success rate of a
given circuit. Sound and complete algorithms are developed for these problems
and their computational complexity is studied.
