抄録
In this paper we report the best estimates and the method to get them of Okumura's problem[10]that is an interval problem of resistive networks. We proof the monotonicity of the problem and estimate the answer using by the signs of the sensitivity. The proof of the monotonicity is main part of this paper. The confluence of the network in Fig.1 makes it equivalent to the monotonicity of the problem that the signe of i_6 and i_7 don't change. The numerical result of Okumura's interval method[10] satisfies the condition.
