In which year did Coulomb arrive at the inverse square law relation?

1. The law predates the discovery of the electron by a century. 2. It was established in the late eighteenth century. 3. Coulomb arrived in 1785 at the inverse square law relation now known as Coulomb's law. 4. So the answer is 1785. _Source: syllabus Physics, Ch 1 'Electric Charges and Fields'_