A tachometer measures, for example it measures the MPH(Miles Per Hour) in a car. So like it measures your speed, so you could be going 100 MPH.
Answer:197.504 N
Explanation:
Given
Two Charges with magnitude Q experience a force of 12.344 N
at distance r
and we know Electrostatic force is given



Now the magnitude of charge is 2Q and is at a distance of 

F'=16F
F'=197.504 N