Count the number of students from UCSD enlisted in the peace corps.
in the peace corps refers to organ = 'peace_corps'; from UCSD refers to school = 'ucsd';
SELECT COUNT(T1.name) FROM enlist AS T1 INNER JOIN enrolled AS T2 ON T1.`name` = T2.`name` WHERE T2.school = 'ucsd' AND T1.organ = 'peace_corps'