How many French customers does Gerard Hernandez take care of?
Gerakd Hermandez is an employee; French customer refers to customer from France where country = 'France'
SELECT COUNT(t1.customerNumber) FROM customers AS t1 INNER JOIN employees AS t2 ON t1.salesRepEmployeeNumber = t2.employeeNumber WHERE t1.country = 'France' AND t2.firstName = 'Gerard' AND t2.lastName = 'Hernandez'