In an oil drop experiment, the following charges (in arbitary units) were found on a series of oil droplets:
2.30 × 10−15, 6.90 × 10−15, 1.38 × 10−14
5.75 × 10−15, 3.45 × 10−15, 1.96 × 10−14
The magnitude of charge on the electron (in the same unit) is: