Can anyone plz

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Domain- all the x-values that can be plugged into the function/ applicable to the function.

x-values in this case are measured in units of time(years) AFTER he deposited the amount.

Therefore, we only have positive x-values because the yearly interest rate in this function is only applicable to a positive number of years. 
The bracket means including zero
The parentheses mean not including zero.
Whenever the infinity symbol(∞) is used it is always accompanied by a parentheses.

[0, ∞) is the answer because infinitely many positive number of years can be plugged into this function.