AAA Co Operates Distribution Centers in the Midwest

Short Answer

AAA Co. operates distribution centers in the Midwest. Three of their centers were recently audited to determine if they are in compliance with company standard billing procedures. According to the auditing firm, a billing had an equal probability of being from each of the three centers. A random sample of the audited billings had the following distribution.
Center 1: 385 billings
Center 2: 305 billings
Center 3: 210 billings
What is the expected value of the number of billings for each center if H₀ (equal probabilities) is true?