Answer:
a
Explanation:
As an estimate, consider the two objects as particles separated by 7m.
Take the universal gravitational constant G as 6.67 × 10^(-11) Nm²/kg²
The required gravitational force
= [6.67 × 10^(-11) × 1 × 28] / 7²
≈ 3.811428571 × 10^(-11) N
= 3.81 × 10^(-11) N (corr. to 3 sig. fig.)
∴ The answer should be a. 3.81
