Give the total number of all graduated students from a 2-year public schools in Alabama in 2011.
number of graduated students refers to grad_cohort; 2-year refers to level = '2-year'; public refers to control = 'Public'; Alabama refers to state = 'Alabama'; in 2011 refers to year = '2011'; reace = 'X' means all students.
SELECT SUM(T2.grad_cohort) FROM state_sector_details AS T1 INNER JOIN state_sector_grads AS T2 ON T2.stateid = T1.stateid WHERE T1.state = 'Alabama' AND T2.year = 2011 AND T1.level = '2-year' AND T1.control = 'Public' AND T2.race = 'X'