Sentence Correction (SC) | Executives and federal officials say that the use of crack and cocaine

GMATNinja KarishmaB

Sentence : Executives and federal officials say that the use of crack and cocaine is growing rapidly among workers, significantly compounding the effects of drug and alcohol abuse, which already are a cost to business of more than $100 billion a year.

To identify the noun for "cost", as is the universal test of ask what to the verb so
what cost(s) business more than $100 billion? The answer (according to me) is "the use of crack and cocaine.
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