code: public Exchange getExchangeInfo(Exchange.Type currency, long quantity) throws GuildWars2Exception {
  		isValueValid(quantity);
  		try {
  			Response<Exchange> response = gw2API.getExchangeInfo(currency.name(), Long.toString(quantity)).execute();
  			if (!response.isSuccessful()) throwError(response.code(), response.errorBody());
  			return response.body();
  		} catch (IOException e) {
  			throw new GuildWars2Exception(ErrorCode.Network, "Network Error: " + e.getMessage());
  		}
  	}
docs: For more info on exchange coins API go <a href="https://wiki.guildwars2.com/wiki/API:2/commerce/exchange/coins">here</a><br/>
  
  @param currency exchange currency type
  @param quantity The amount to exchange
  @return the current coins to gems exchange rate
  @throws GuildWars2Exception see {@link ErrorCode} for detail
  @see Exchange Exchange info