Answer:
a.
![F=1.03* 10^(-7)N](https://img.qammunity.org/2021/formulas/physics/college/z3vvbdc79kg1essts5km7e2ujxpp9bptu5.png)
b.Repulsive
Step-by-step explanation:
We are given that
![q_1=7.45nC=7.45* 10^(-9)C](https://img.qammunity.org/2021/formulas/physics/college/npt4t9f3v9k49ge9sc2skrpgngw8dio5mo.png)
![1nC=10^(-9)C](https://img.qammunity.org/2021/formulas/physics/college/2ine9j3vndkky5f5mvm71w5yey7itywv68.png)
![q_2=4.22nC=4.22* 10^(-9)C](https://img.qammunity.org/2021/formulas/physics/college/ynixin1setcpo818q8qycuuav80x97l60m.png)
r=1.66m
We know that
Electrostatic force =
![F=k(q_1q_2)/(r^2)](https://img.qammunity.org/2021/formulas/physics/high-school/igajcb2d1g6uprm6t1m1e0uh69jh7978lc.png)
r=Distance between
![q_1\;and\;q_2](https://img.qammunity.org/2021/formulas/physics/college/eeqffrswmog3yghphamte7mfpbqp5klu6p.png)
k=Constant=
![9* 10^9Nm^2C^(-2)](https://img.qammunity.org/2021/formulas/physics/college/kt2d5tiyuyr32s04vezz107gqh0230sumk.png)
Using the formula
a.The magnitude of the electrostatic force=
![F=(9* 10^9* 7.45* 10^(-9)* 4.22* 10^(-9))/((1.66)^2)](https://img.qammunity.org/2021/formulas/physics/college/1wxzhcpw3z3cmrxdzmqwbcntf9nf7g2q8p.png)
The magnitude of the electrostatic force=
![F=1.03* 10^(-7)N](https://img.qammunity.org/2021/formulas/physics/college/z3vvbdc79kg1essts5km7e2ujxpp9bptu5.png)
b.Both charge are positive .We know that when like charges repel each other and unlike charges attract to each other.
Therefore, the force between given charges is repulsive.