*2.31 The circuit in Fig. P2.31 can be considered to be an extension of the circuit in Fig. 2.8. (a) Find the resistances looking into node 1, R1; node 2, R2; node 3, R3; and node 4, R4. (b) Find the currents I1, I2, I3, and I4, in terms of the input current I. (c) Find the voltages at nodes 1, 2, 3, and 4, that is, V1, V2, V3 , and V4 in terms of (IR).