20 mL之50% magnesium sulfate injection含有多少mEq之鎂離子？（mol wt of \mathrm{MgSO}_{4}·\mathrm{7H}_{2}O＝246）
\mathrm{MgSO}_{4}
\mathrm{7H}_{2}
40.7
81.3
162.6
166.6
