A cell with negligible internal resistance is joined to a resistor network and a voltmeter, as shown. The voltmeter gives a reading of zero. What is the value of the resistance of resistor $R$?
- A$1.20\,\Omega$
- B$1.80\,\Omega$
- C$7.20\,\Omega$
- D$14.4\,\Omega$