A certain organic compound $O$ has a solubility in acetonitrile of $0\mathrm{.}511\frac{g}{mL}$ at $10.C.$ Calculate the mass of $O$ required to prepare $5\mathrm{.}0L$ of a saturated solution of $O$ in acetonitrile at this temperature.

Be sure your answer has the correct unit symbol and $2$ significant digits.