TA voltmeter indicates that the potential at a location between two parallel conducting plates is $7\mathrm{.}8V,$ where the negatively charged plate is at $0V.$ If the plates are $22mm$ apart and are connected to a $23-V$ battery, how far is the measurement location from the negative plate?

Report your answer is units of millimeters. For example, if your calculations produce a value of $1\mathrm{.}23mm,$ enter your answer as $1\mathrm{.}23.$