How do i Figure out Excess return for each month for VTI???

DUE IN A COUPLE HOURS NEED HELP

month-date	VTI	Rf	CPI
12-10			219.2
1-11	2.05%	.008%	220.2
2-11	3.7%	.013	221.3
3-11	.42%	.006	223.5
4-11	2.89	.003	224.9
5-11	-1.06	.002	226
6-11	-1.8	.003	225.7
7-11	-2.26	.002
8-11	-6.09	.003
9-11	-7.58
10-11	11.36
11-11	-.37