In an oil drop experiment, the following charges (in arbitrary units) were found on a series of oil — Atomic Structure Chemistry Question

Question

In an oil drop experiment, the following charges (in arbitrary units) were found on a series of oil droplets: $4.5 \times 10^{-18}$, $3.0 \times 10^{-18}$, $6.0 \times 10^{-18}$, $7.5 \times 10^{-18}$, $9.0 \times 10^{-18}$. The charge on electron (in the same unit) should be