Do we have an obligation, as some green activists believe, to restore environmental conditions to the state which they were before human intervention?

No we don't have no obligation

Explanation:

But trust me if we don't help your town will suck and pollution will grow. So we should help but don't need to since we actually pay money for this changes even green activist pay. It is called tax.  

the amount of the purse is, $120.

tax rate =9%

first find the the total tax she paid on the amount is equal to the 9% of $120 i.e,

now,

total amount paid by shalika = $120 +$10.8 = $130.8