instruction: What are the coupon amount of the coupons owned by both good and bad customers?
response: SELECT T1.coupon_amount FROM discount_coupons AS T1 JOIN customers AS T2 ON T1.coupon_id = T2.coupon_id WHERE T2.good_or_bad_customer = 'good' INTERSECT SELECT T1.coupon_amount FROM discount_coupons AS T1 JOIN customers AS T2 ON T1.coupon_id = T2.coupon_id WHERE T2.good_or_bad_customer = 'bad'