The diagram contains three resistors arranged in series and joined to a battery. A voltmeter is connected across each resistor, and two of the voltages are given. What is the potential difference (p.d.) across the resistor $R$?
- A$12\,\text{V}$
- B$22\,\text{V}$
- C$30\,\text{V}$
- D$68\,\text{V}$