diff --git a/_modules/week-15.md b/_modules/week-15.md
index b7f26ab..7b640f3 100644
--- a/_modules/week-15.md
+++ b/_modules/week-15.md
@@ -14,7 +14,9 @@ Apr 23
 
 Apr 25
 : **Lecture 27**{: .label .label-lecture} [Intro to LLMs and Conclusion](lecture/lec27)
-: **Exam Prep 11**{: .label .label-vit } PCA
+: **Lecture Participation 27**{: .label .label-survey } [Lecture Participation 27](https://app.sli.do/event/pxVnXajRJK4kjXDRX1c7Me/login?redirect_url=https%3A%2F%2Fapp.sli.do%2Fevent%2FpxVnXajRJK4kjXDRX1c7Me)
+: **Exam Prep 11**{: .label .label-vit } [PCA and Clustering](https://drive.google.com/file/d/1ghooCdqS7Zj2ZHaIUTUUyT7fJRZcbxNU/view?usp=sharing)
+
 
 Apr 26
 : **Lab 13**{: .label .label-lab } Clustering (due Apr 30)