In Accordance with Wilson and MacArthur's Theory of Island Biogeography

In accordance with Wilson and MacArthur's theory of island biogeography, the following equations represent the extinction and immigration rates of species of spiders on a small island. (I = immigration rate of species per year; E = extinction rate of species per year; S = number of species currently on the island.)
I = 3 ? 0.1S
E = 0.2S
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Based on these equations, what is the expected equilibrium species diversity on this island?

A) 3
B) 6
C) 10
D) 20