날짜 품목 박스수 수량  단가  공급가액 세액 4/4.  초코.    5     402 2400

 물건이 불량인게 있어서, 50%공제해주는것도 있고, 1/3로도 공제를 해준게 있는데 수식을 =if(수량="불량",단가*50%,"") 썼는데 자꾸 수식이 틀렸다고 나와요ㅜㅡㅠ 왜 그런가요???
 엑셀 잘 하시는 분 계시면 세세히 어디가 틀렸는지부터 정정을 어떻게 하는지도 알려주세요ㅜㅜ 정말 어렵네요;;;