Two charges $\backslash ($ A $\backslash )$ and $\backslash ($ B $\backslash )$ are fixed in place, at different distances from a certain spot. At this spot the potentials due to the two charges are equal. Charge $\backslash ($ A $\backslash )$ is $0\mathrm{.}150$ m from the spot, while charge $\backslash ($ B $\backslash )$ is $0\mathrm{.}640$ m from it$.$ Find the ratio $\backslash ($ q$\_\{$B$\}/$ q$\_\{$A$\}\backslash )$ of the charges.