Two charges, when separated by a distance $R,$ produce a force $F$ on each other. If the separation is increased to $1\mathrm{.}7R,$ what is the new force?

$($a$)0\mathrm{.}12F$

$($b$)0\mathrm{.}60F$

$($c$)2\mathrm{.}9$ F

$($d$)0\mathrm{.}40$ F

$($e$)0\mathrm{.}35$ F