Answer:
11.44pC.
Step-by-step explanation:
F = kq1q2/r^2
q2 = Fr^2/kq1
= 4.5 x 0.31^2/4.2x 9 x 10^9
= 1.144 x 10^-11C
= 11.44pC
The sign is minus since they attracted to each other
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