Gerald is responsible for keeping track of his agencies , or the amount of client money his agency spends on media purchases and other equivalent activities.

Billings

Explanation:

Billings is the amount of money invoiced that is to be paid out for a good or service or the amount of money collected from a customer.

Billings is the right answer because logically from the question, it is the term that defines the sentence scenario "the amount of client money his agency spends on media purchases and other equivalent activities."

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