(a) In the figure what value must R have if the current in the circuit is to be 1.2 mA? Take $1 = 2.3 V, &2 = 4.7 V, and r1 = 12 = 3.7 0. (b) What is the rate at which thermal energy appears in R? 12 R (a) Number i Units v (b) Number i Units v