$(function() {
	var suffix = "_over";
	$('.btn_img').hover(function () {
    		var thesrc = $(this).attr('src');	
    		var name = thesrc.substring(0, thesrc.lastIndexOf('.'));
    		var extension = thesrc.substring(thesrc.lastIndexOf('.'));
    		$(this).attr('src', name + suffix + extension);
    	}, function () {
    		var thesrc = $(this).attr('src');
    		var name = thesrc.substring(0, thesrc.lastIndexOf('.') - suffix.length);
    		var extension = thesrc.substring(thesrc.lastIndexOf('.'));
    		$(this).attr('src', name + extension);
    	}
    );
});