What is the first name of students enrolled in class ACCT-211 and got grade C?
select t3.stu_fname from class as t1 join enroll as t2 on t1.class_code = t2.class_code join student as t3 on t2.stu_num = t3.stu_num where t1.crs_code = 'ACCT-211' and t2.enroll_grade = 'C'