The output is the inverted carry of carry inputs
a and b
and the carry of input c.
The stage efforts for pin c
is 1.6, 1.9 and 2.4 for the x05,
x1 and x2 drive strengths respectively.
The cells here use a P/N ratio of about 2.
z:((a*b)+(a*c')+(b*c'))'
cell width
power
Generic 0.13um typical timing (ps & ps/fF),
pin c.