The diagram illustrates a section of a circuit that includes an ammeter, a voltmeter and a resistor $R$. The ammeter and the voltmeter are placed in the correct positions for finding the resistance of $R$. Which expression gives the value of $R$?
- Areading of meter P $\div$ reading of meter Q
- B$(\text{reading of meter P})^2 \times \text{reading of meter Q}$
- Creading of meter Q $\times$ reading of meter P
- Dreading of meter Q $\div$ reading of meter P