diff --git a/E04SumCalculator/.idea/deploymentTargetDropDown.xml b/E04SumCalculator/.idea/deploymentTargetDropDown.xml
index 0c0c3383890637b4721df1f49d0b229e55c0f361..940abb4b3558f4981dbbb29f6f0f9d91c65aa45c 100644
--- a/E04SumCalculator/.idea/deploymentTargetDropDown.xml
+++ b/E04SumCalculator/.idea/deploymentTargetDropDown.xml
@@ -3,7 +3,20 @@
   <component name="deploymentTargetDropDown">
     <value>
       <entry key="app">
-        <State />
+        <State>
+          <runningDeviceTargetSelectedWithDropDown>
+            <Target>
+              <type value="RUNNING_DEVICE_TARGET" />
+              <deviceKey>
+                <Key>
+                  <type value="SERIAL_NUMBER" />
+                  <value value="kf5hy9pzzhq4fece" />
+                </Key>
+              </deviceKey>
+            </Target>
+          </runningDeviceTargetSelectedWithDropDown>
+          <timeTargetWasSelectedWithDropDown value="2023-11-27T13:19:36.735951762Z" />
+        </State>
       </entry>
     </value>
   </component>
diff --git a/E04SumCalculator/README.md b/E04SumCalculator/README.md
new file mode 100644
index 0000000000000000000000000000000000000000..14686d0c863e2ec2131d5a2a285a58488f8ee79d
--- /dev/null
+++ b/E04SumCalculator/README.md
@@ -0,0 +1 @@
+<iframe width="560" height="315" src="https://www.youtube-nocookie.com/embed/cVrQ5wwOCjA?si=aCnfhDXenqp9jv-1" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share" allowfullscreen></iframe>
diff --git a/README.md b/README.md
index 1a317c9831e8eb4b6b643ad8f6961e834e8437cd..2d0c56f3237974412eede49850cd45d9d6b5cbea 100644
--- a/README.md
+++ b/README.md
@@ -5,8 +5,9 @@ Iftakhar Husan
 - [Exercise 1][ex1]
 - [Exercise 2][ex2]
 - [Exercise 3][ex3]
-
+- [Exercise 4][ex4]
 
 [ex1]: ./e01-first-application/
 [ex2]: ./e02-build-ui-with-layout-editor-1/
 [ex3]: ./E03BuildUIWithLayoutEditor2/
+[ex4]: ./E04SumCalculator/