[填空题]
Estimate the number oayfieh5.vtor f/ 9aq1rd6k v /-8 :iqi/vccdyr(baf+ pova))3e -m x8f (a) moles, $ \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