The exponential function given is \( y = 4 \left( \frac{6}{1} \right)^x \), which simplifies to \( y = 4 \cdot 6^x \).
In an exponential function of the form \( y = a \cdot b^x \), the growth rate is determined by the base \( b \). Here, \( b = 6 \).
The growth rate can also be represented as \( r = b - 1 \). Thus:
\[ r = 6 - 1 = 5 \]
So, the growth rate of the function is 5.