Question: What's the average number of graduates for Central Alabama Community College in the 3 consecutive years from 2011 to 2013?
SQL: SELECT AVG(T2.grad_cohort) FROM institution_details AS T1 INNER JOIN institution_grads AS T2 ON T2.unitid = T1.unitid WHERE T1.chronname = 'Central Alabama Community College' AND T2.year IN (2011, 2012, 2013) AND T2.gender = 'B' AND T2.race = 'X'