Answer:
The figure of speech in this sentence is a hyperbole.
Explanation:
'Mountain of bills' is an exaggeration to strongly point out something. It doesn't have to be taken literally. These kinds of sentences create strong impressions or feelings by exaggerating a word or phrase in the sentence.
You cannot take this extravagant statement literally, as it does not provide any concrete meaning. It is present in the sentence to only emphasize on the incident strongly.
