diff --git a/ch04.r b/ch04.r
index 22a4fc6..0c922d8 100644
--- a/ch04.r
+++ b/ch04.r
@@ -1,6 +1,23 @@
+#############
 # Chapter 4.3 (Cumulative Distribution Function)
 
-## 4.10 CDF of a Uniform Random Variable
+## CDF of a Gaussian Mixture
+# R code to generate the PDF and CDF
+library(EnvStats)
+x = seq(-5, 10, (5+10)/1000)
+x = sort(x)
+f = dnormMix(x, 0, 1, 5, 1, p.mix=c(0.7))
+plot(x,f, xlim=c(-5,10), ylim=c(0,0.4), type="n")
+grid()
+lines(x, f, lwd=4, col="blue")
+polygon(c(min(x), x[x<=0.8]), c(f[x<=0.8], 0), col="lightblue")
+
+F = pnormMix(x, 0, 1, 5, 1, p.mix=c(0.7))
+plot(x, F, xlim=c(-5,10), ylim=c(0,0.4), type="n")
+
+# R code to generate the PDF and CDF
+
+## CDF of a Uniform randow variable
 
 # R code to generate the PDF and CDF
 x = seq(-5, 10, (5+10)/1500)
@@ -11,7 +28,7 @@ lines(x, f, lwd=5)
 plot(x, F, type="n")
 lines(x, F, lwd=5)
 
-## 4.11 CDF of an exponential random variable
+## CDF of an exponential random variable
 
 # R code to generate the PDF and CDF
 x = seq(-5, 10, (5+10)/1500)
@@ -22,6 +39,7 @@ lines(x, f, lwd=5)
 plot(x, F, type="n")
 lines(x, F, lwd=5)
 
+#############
 # Chapter 4.5
 
 # Generate a uniform random variable