I'm reading a textbook where the following inequality $$\mu_{ig}< v_a - v_b$$ is given and $\mu_{ig}$ is distributed uniformly on the interval $[-\frac{1}{2\omega_g},\frac{1}{2\omega_g}]$. The expectation given is: $$ \omega_g[v_a-v_b-(-\frac{1}{2\omega_g})] $$
I know that the expectation is $\frac{b+a}{2}=0$ so I don't understand where $\omega_g$ and the last $(-\frac{1}{2\omega_g})$ term in the expectation is coming from.