Terminal voltage of the battery

A coil of 8 ohm resistance is in parallel with a coil of 20ohm resistance. The combination is connected in series with a thrid coil of 12ohm resistance. If the whole circuit is connected across the battery, having an e.m.f. of 30V and an intedrnal resistance of 2ohm. What is the terminal voltage of the battery?

Please show calculations.

30 * (1 - 2/(8*20/(20+8)+12+2))
= approx 26.96V

voltage dropped across internal resistance = (battery voltage) * (internal resistance)/(total resistance)

1

1.2 volts per cell on a 12v battery