diff --git a/education/software development/ECE1400/Chapter 15 Exercises.md b/education/software development/ECE1400/Chapter 15 Exercises.md
index 90c787c..f6c0577 100644
--- a/education/software development/ECE1400/Chapter 15 Exercises.md	
+++ b/education/software development/ECE1400/Chapter 15 Exercises.md	
@@ -56,7 +56,7 @@ demo: main.o f1.o f2.o
 main.o: main.c f1.h
 	gcc -c main.c
 
-f1.o: f1.c f1.h
+f1.o: f1.c f1.h f2.h
 	gcc -c f1.c
 
 f2.o: f1.o f2.c f2.h
@@ -72,9 +72,12 @@ f2.o: f1.o f2.c f2.h
 
 > (b). If `f1.c` is changed after the program has been built, which files need to be recompiled?
 
-All dependents of `f1.c` and `f1.c`, in this case `f1.c`, `main.c`, and `f2.c` (including header files).
+All dependents of `f1.c` and `f1.c`, in this case `f1.c`, `main.c`, and `f2.c`.
 
 > (c). If `f1.h` is changed after the program has been built, which files need to be recompiled?
 
+All source files.
+
 > (d). If `f2.h` is changed after the program has been built, which files need to be recompiled?
 
+