The data below presents monthly closing prices of Standard & Poors 500 Index, Wal-Mart, and Target to calculate the holding-period returns for the 24 months from May 2013 through May 2015

	Month	S&P500	Walmart	Target
2013	May	1.631	74,84	69,50
	June	1.606	74,49	68,86
	July	1.684	77,94	71,25
	August	1.633	72,98	63,31
	September	1.682	73,96	63,98
	October	1.757	76,75	64,79
	November	1.806	81,01	63,93
	December	1.848	78,69	63,27
2014	January	1.783	74,68	56,64
	February	1.859	74,70	62,54
	March	1.872	76,43	60,51
	April	1.884	79,71	61,75
	May	1.924	76,77	56,76
	June	1.960	75,07	57,95
	July	1.931	73,58	59,59
	August	2.003	75,50	60,07
	September	1.972	76,47	62,68
	October	2.018	76,27	61,82
	November	2.068	87,54	74,00
	December	2.059	85,88	75,91
2015	January	1.995	84,98	73,61
	February	2.105	83,93	76,83
	March	2.068	82,25	82,07
	April	2.086	78,05	78,83
	May	2.182	75,86	79,29

Calculate the holding-period returns for the 24 months from May 2013 through May 2015. Calculate the average monthly holding-period returns and the standard deviation of these returns for the S&P Index, Wal-Mart, and Target. Please compare the results obtained for these three series.