Magento – Custom REST API – resource not found

I have followed the tutorial and making a simple REST API.

api2.xml FILE

<?xml version="1.0"?>
<config>
    <api2>
        <resource_groups>
            <custac translate="title" module="sharan">
                <group>sharan</group>
                <title>Abandoned Cart</title>
                <sort_order>10</sort_order>
            </custac>
        </resource_groups>

        <resources>
            <custac translate="title" module="sharan">
                <group>custac</group>
                <model>sharan/api2_restapi</model>
                <title>Abandoned cart info</title>
                <sort_order>2</sort_order>
                <privileges>
                    <admin>
                        <create>1</create>
                        <retrieve>1</retrieve>
                        <delete>1</delete>
                    </admin>                   
                </privileges>
                <routes>
                    <route>
                        <route>abcart</route>
                        <action_type>entity</action_type>
                    </route>
                </routes>
                <versions>1</versions>
            </custac>
        </resources>
    </api2>
</config>

Model file – Api2_Restapi

<?php 
class Ziffity_Sharan_Model_Api2_Restapi extends Mage_Api2_Model_Resource{
    public function _retrieve(){
        return json_encode(array("value"=>"Hello World"));
    }
}///end of class//
?>

V1.php file

<?php
class Ziffity_Sharan_Model_Api2_Rest_V1 extends Ziffity_Sharan_Model_Api2_Restapi{
    public  function _retrieve(){
        return json_encode(array("value"=>"Hello World"));
    }
} 
?>