and gives the minimum at $\Delta \cong 0.082$. The curves of $E_g/N_s$ for the $s$- and $s^*$-wave gap functions have definite positive slopes at small $\Delta$ and are extrapolated for $\Delta = 0$ to $\sim -0.7354$ and $\sim -0.7353$, respectively, which are practically equal. These values are slightly higher than the value $\sim -0.73605$ given by extrapolating the $d$-wave fitting parabola to $\Delta = 0$. The normal state value of $E_g/N_s = - 0.73585$ lies between the two groups of extrapolated values. The differences are due to a kind of size effect, as was explained in the previous report \[\]. These differences in the case of $10 \times 10$ lattice are much smaller than the depth of the minimum of the $d$-wave curve.

The energy gain per site in the $d$-wave state was obtained from the parabola fitting to the energy-versus-$\Delta$ curve as its depth of the minimum in reference with the intersection of the fitting curve with the vertical axis as $\sim 0.00155$/site. It is five times larger than that for $N_e = 32$ and $N_e = 36$. This suggests that the size effect is considerable in the $6 \times 6$ system. This energy gain per site in the 