3.7 a) In the circuits in Fig. P3.7(a)-(d), find the equiv- PSPICE alent resistance seen by the source. MULTISIM b) For each circuit find the power delivered by the source. Figure P3.7 45 0 20 0 WW 25 0 30 0 60 0 18 0 30 V 15 0 3 60 0 50 0 50 0 80 mA 60 0 40 0 75 0 4 120 10 0 20 0 20 0 30 0 (a) (b)