What would be the orbital period of a star in the outskirts of a spiral galaxy that has a diameter of $92$ thousand light years and a total mass of $1\mathrm{.}34$x$10\mathrm{¹}$² MSun. We know that $1$ light year $=9\mathrm{.}46$x$10\mathrm{¹}$⁵ m and $1$ MSun $=1\mathrm{.}99$x$10\mathrm{³}\mathrm{⁰}$ kg is the Sun's mass. Give your answer in My $($mega$-$years or millions of years$).$