Answer:
[tex]F = 7.7*10^{-10}N[/tex]
Explanation:
You need to be careful with units for this problem. The force will be:
[tex]F =\frac{K*m1*m2}{d^2}[/tex]
[tex]F=\frac{6.67259 * 10^{-11}*1.56*21.1*10^{-3}}{(5.34*10^{-2})^2}[/tex]
[tex]F=7.7*10^{-10}N[/tex]