cleaning up makefile stuff for ex22

Makefile

@@ -3,13 +3,9 @@ CFLAGS=-Wall -g -DNDEBUG
 EXERCISES = $(patsubst %.c,%,$(shell ls ex*.c | egrep -v "ex(19|22)"))
 
 
-all: $(EXERCISES) ex22_main
+all: $(EXERCISES)
 	$(MAKE) -f ex19.mk
-
-
-ex22_main: ex22.c ex22_main.c ex22.h
-	$(CC) $(CFLAGS) -c -o ex22.o ex22.c
-	$(CC) $(CFLAGS) ex22_main.c ex22.o -o $@
+	$(MAKE) -f ex22.mk
 
 
 test: all
@@ -19,6 +15,7 @@ test: all
 clean:
 	rm -f $(EXERCISES)
 	$(MAKE) -f ex19.mk clean
+	$(MAKE) -f ex22.mk clean
 
 
 .PHONY: all test clean

ex22.mk

@@ -0,0 +1,10 @@
+all: ex22_main
+
+
+ex22_main: ex22_main.o ex22.o
+
+
+clean:
+	rm -f ex22_main ex22.o ex22_main.o
+
+.PHONY: all clean