A charge of +6 micro-coulombs lies on the x axis at x = 0 m. An unknown charge lies on the x axis at x = +0.19 m. The amount of electric force on the charge at x = 0 m is 8.3 Newtons in the positive x direction. What is the unknown charge at x = +0.19 m in micro-coulombs? If negative, indicate so with a negative sign, but omit a sign if positive.