Widgets of Type A arrive with Poisson Process with arrival rate $\lambda_A$, and, for Type B, with arrival rate $\lambda_B$ (independent).
During t, there have been b arrivals of Type B. What are the expected arrivals of Type A+B in time frame t?
Does one simply take the given value b, and add to that the expected arrivals for process A?:
$b+t \times \lambda_A$