In which episode of ipartment did Brother Zeng eat mint mustard?

Ipartment 4 episode 20 The Pursuit of Happyness (1) Zhang Wei and Meijia are questioning Yifei about the Christmas tree in her room. Yifei didn't answer directly, but made up a story to hide the truth. But Yifei's winning the prize made her feel very uneasy. She decided to take Meijia's advice and invite Ceng Xiaoxian to dinner. As a result, Yifei stood Ceng Laoshi up, which made Ceng Laoshi very embarrassed. Zi Qiao is hooking up with a new beauty again. This time, menstruation became Zi Qiao's best companion. Meijia and Theway think that Yifei and Ceng Laoshi are not normal recently, and think that the Prince Charming Yifei met on Christmas Eve is Ceng Laoshi. They decided to test it with experiments. As a result, unwitting Ceng Laoshi ate a hamburger with mustard and mint, and Yifei sent mouthwash, which made Ceng Laoshi feel that Yifei was fooling himself. Youyou and Zi Qiao continue to search for information about their sister, and they find a mysterious Weibo. The contents recorded above are just like the contents of the death note, and Lv Ziqiao completely collapsed.