Population Growth Rate Question?
As you have phrased it, the question can be understood in two ways. 


The population size at t+1 is 350, after births, deaths and migration have taken place.
The population size is 350 after deaths, but you also have to take births and migration into account to calculate population size at t+1


For alternative 1 the growth rate is:

$pgr = \frac{(230+21)-(488+13)}{600} = -0.417$, 

with $\Delta N=-250 \Rightarrow -250 = 230+21-deaths-13$

For alternative 2 the growth rate is:

$pgr = \frac{(230+21)-(250+13)}{600} = -0.02$