Final answer:
The appropriate operator for determining if the retail price of a book is at least $24.00 is the 'greater than or equal to' operator, denoted by '≥'.
Step-by-step explanation:
To determine whether the retail price of a book is at least $24.00, the most appropriate operator to use would be the 'greater than or equal to' operator, which is denoted by '≥'. In mathematical terms, if the retail price of the book is represented by 'P', then the expression to determine if the book's price meets the criteria would be 'P ≥ 24.00'. This operator allows us to check whether the price is greater than or equal to $24.00, satisfying the requirement for being at least $24.00.