[填空题]
Estimate the number of (a) mo1y, wu8hehvt ( ik*c)wlesihwy tnxnsx2q i39 75), $ \times10^{22 }$ moles and (b) molecules of water in all the Earth’s oceans. Assume water covers 75% of the Earth to an average depth of 3 km. $\approx$ $ \times10^{46 }$ molecules