Let C1 be a circuit without input variables and with output variable y1 and register r1.
The control function for the output variable transition is y1'=r1, i.e., on the next step y1 is equal to the value of r1 from the previous step. The control function for the register variable transition is r1' = !r1.

Circuit C2 has input variable x2, output variable y2, and register variable r2 with the
control functions:
y2'= x2' OR r2
r2'=x2' OR r2

Model the synchronous composition of these two circuits.

Use the variable names y1, r1, x2, y2, and r2
