A circuit consists of eight (8) devices as shown. The values of the voltages measured across the nodes are $V_{af} = 12V$, $V_{dc} = 4V$, $V_{cb} = 4V$, $V_{ba} = -2V$, $V_{af} = 6V$, $V_{de} = 6V$, $V_{ef} = 6V$, $V_{eb} = 2V$. The currents through the devices are also provided.
a. Find $V_{ea}$, $V_{bf}$, $V_{db}$, and $V_{cf}$.
b. Find the power for each device and determine if the device is sourcing or dissipating (sinking) energy.