Cornering button to bottom left android

I am trying to do a menu exactly like CandyCrush's: Two buttons (play and connect) in the center and then right at the bottom left, there's another button (the CC's arrow). I manage to position the first to buttons, but I am unable to position the last one at the bottom left of my activity. How can I position it? This is my xml and I use Relative Layout.

<RelativeLayout xmlns:android="http://ift.tt/nIICcg"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent">

<ImageView
    android:id="@+id/balao"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentTop="true"
    android:layout_centerHorizontal="true"
    android:adjustViewBounds="true"  
    android:scaleType="fitCenter"  
    android:background="@null"
    android:maxWidth="200dp"  
    android:maxHeight="180dp"
    android:layout_weight="1"
    android:layout_marginTop="10dp"
    android:layout_marginBottom="35dp"
    android:src="@drawable/balao" />
<ImageButton
    android:id="@+id/play"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:adjustViewBounds="true"
    android:layout_centerHorizontal="true"
    android:maxWidth="80dp"  
    android:maxHeight="80dp"
    android:background="@android:color/transparent"   
    android:layout_below="@+id/balao"
    android:layout_weight="1"
    android:layout_marginBottom="10dp"
    android:src="@drawable/playbutton" />
<ImageButton
    android:id="@+id/tutor"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:adjustViewBounds="true"
    android:layout_below="@+id/play"  
    android:layout_centerHorizontal="true"
    android:maxWidth="50dp"  
    android:maxHeight="50dp"
    android:background="@android:color/transparent"   
    android:layout_weight="1"
    android:src="@drawable/tutor" />

<ImageButton
        android:id="@+id/corner"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:adjustViewBounds="true"
        android:layout_alignParentBottom="true"
        android:layout_alignParentLeft="true"
        android:src="@drawable/corner"/>
</RelativeLayout>