Paragraph: The following questions are concerned with experiments...

Paragraph: The following questions are concerned with experiments on the characterization and use of a moving coil galvanometer. The series combination of a variable resistance $R$, one $100 \Omega$ resistor and a moving coil galvanometer is connected to a mobile phone charger having negligible internal resistance. The zero of the galvanometer lies at the centre and the pointer can move 30 divisions full scale on either side depending on the direction of current. The reading of the galvanometer is 10 divisions and the voltages across the galvanometer and $100 \Omega$ resistor are respectively 12 mV and 16 mV .Question: The figure of merit of the galvanometer in microampere per division is