How many white patients have the reason code of 10509002?
white refers to race = 'white'; reason code of 10509002 refers to careplans.REASONCODE = '10509002';
SELECT COUNT(DISTINCT T1.PATIENT) FROM careplans AS T1 INNER JOIN patients AS T2 ON T1.PATIENT = T2.patient WHERE T2.race = 'white' AND T1.REASONCODE = '10509002'