public ListingDurations RetrieveDurationOptionsForCategory(string categoryNumber)
{
var url = String.Format(Constants.Culture, "{0}/{1}/{2}{3}", Constants.CATEGORIES, categoryNumber,
Constants.DURATIONS, Constants.XML);
var getRequest = _connection.UnauthenticatedConnection(url);
var xml = getRequest.ToString();
return Deserializer<ListingDurations>.Deserialize(new ListingDurations(), xml);
}