Nobody "knows" the answer, but many people know how to find it, and there's no reason that you shouldn't be one of them.
Right there, on the screen, it gives you the complete formula to use, and then it gives you all the numbers to write into the formula. All you need to do is write the numbers they gave you into the formula that they gave you, and do the arithmetic. There's isn't even any Physics here ! Just arithmetic, and you can do it with your calculator.
The formula is F = k · q₁ · q₂ / r²
The 'q's are 0.0042 and -0.005 , and 'r' is 0.003 .
Please ! Don't embarrass both of us. Write the 'q's and the 'r' into the formula, turn the crank, and match the answer on your calculator to the choices.
