Both batteries in Figure a are ideal. Emf ? 1 of battery 1 has a fixed value,

Question:

Both batteries in Figure a are ideal. Emf ?₁ of battery 1 has a fixed value, but emf ?₂ of battery 2 can be varied between 1.0 V and 10 V. The plots in Figure b give the currents through the two batteries as a function of ?₂. The vertical scale is set by i_s = 0.20 A. You must decide which plot corresponds to which battery, but for both plots, a negative current occurs when the direction of the current through the battery is opposite the direction of that battery's emf. What are?

(a) Emf ?₁,

(b) Resistance R₁, and