To find the amount of money in the bank at the end of 5 years using the given function \( f(x) = 4000(1.06)^x \), where \( x \) represents the number of years since the investment, we need to evaluate \( f(5) \).
Let's calculate \( f(5) \):
\[ f(5) = 4000(1.06)^5 \]
First, we need to calculate \( (1.06)^5 \):
\[ (1.06)^5 \approx 1.338225 \]
Now, substituting this back into the function:
\[ f(5) = 4000 \times 1.338225 \]
Calculating this gives:
\[ f(5) \approx 5352.90 \]
Thus, at the end of 5 years, there will be approximately \( \boxed{5352.90} \) dollars in the bank.