how to find gravity form dropdown selected option in mail notification

<select name=”input_20″ id=”input_5_20″ class=”medium gfield_select” tabindex=”5″><option value=”” selected=”selected”>Please choose </option> <option value=”test1″>Test1</option> <option value=”test2″>Test2</option> <option value=”test3″>Test3</option> <option value=”test4″>Test4</option> <option value=”test5″>Test5</option>…

how to set adminnotification mail subject to be custum depend on form dropdown option value

am using a gravity-form in this we have one drop down like <select name=”input_20″ id=”input_5_20″ class=”medium gfield_select” tabindex=”5″><option value=”” selected=”selected”>Please…