The Safe Drinking Water Act $($SDWA$)$ has set a limit for mercury $,$ molar mass $=200\mathrm{.}592\frac{g}{m}ol)$ to be $2\mathrm{.}0ppb$ by mass in drinking water. Water suppliers must periodically test their water to ensure that mercury levels do not exceed this limit$.$ A $10\mathrm{.}0mL$ sample of drinking water $($density $=1\mathrm{.}00\frac{g}{m}L)$ is determined to have a concentration of $4{10}^{-8}M.$

According to the SDWA, is this water safe to drink?