diff --git a/education/software development/ECE1400/Chapter 15 Exercises.md b/education/software development/ECE1400/Chapter 15 Exercises.md
index 41822ad..222d970 100644
--- a/education/software development/ECE1400/Chapter 15 Exercises.md	
+++ b/education/software development/ECE1400/Chapter 15 Exercises.md	
@@ -48,4 +48,10 @@ Macro invocations are evaluated sequentially, and so if `DEBUG` was defined afte
 ---
 
 > **6.** The following questions refer to the program described in Exercise 5.
-> (a). Wh
+> (a). Which files need to be compiled when the program is built for the first time?
+
+> (b). If `f1.c` is changed after the program has been built, which files need to be recompiled?
+
+> (c). If `f1.h` is changed after the program has been built, which files need to be recompiled?
+
+> (d). If `f2.h` is changed after the program has been built, which files need to be recompiled?