Chapter 7 Exponential and Logarithmic Functions - 7.1 Graph Exponential Growth Functions - Guided Practice for Example 4 - Page 480: 5

The initial amount is $527$, the percent increase is $1.39-1=0.39$, and the growth factor is $1.39$.

If for an exponential function $y=ab^x$ $a\gt0,b\gt1$, then it is an exponential growth function, and $b$ is the growth factor. Following the example, the initial amount is $527$, the percent increase is $1.39-1=0.39$, and the growth factor is $1.39$.