Chapter 5 - 5.5 - Exponential and Logarithmic Models - 5.5 Exercises - Page 406: 34

$ y \approx 396.85$ or, $ y \approx 397$

We have $y=ae^{bx}$ $2y=ye^{9b}$ or, $2 = e^{9b}$ Take the $\log$ on each side. $\ln 2 =\ln e^{9b} \implies b=\dfrac{\ln 2}{9}$ Now, $y=250 e^{6b} = 250 \times e^{\dfrac{6\ln 2}{9}} $ So, $ y \approx 396.85$ or $ y \approx 397$