What formula can be used to calculate [h30+]

[H3O+] is just the same with [H+]. There are quite a few relationships between [H+] and [OH−] ions. And because there is a large range of number between 10 to 10-15 M, the pH is used. pH = -log[H+] and pOH = -log[OH−]. In aqueous solutions, [H+ ][OH- ] = 10-14
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The answer is b because c don't explain why the moths are on them and it isn't a because as we know only one species of moth does this

Answerhund's rule;