Look up a cell in column and add another

Hello,
I'm trying to look up an item in one column and see how many were sold from another column. The columns are side by side. There are 5 items sold in the first column, and trying to find out many total in the other. Or, like how many were sold on a Monday for an entire year.
It would look like this.
A B
Day Sold
Mon 110
Tues 50
Wed. 10
Thurs 20
Frid 30
Sat. 40
Sun 50
Mon 60
Tues 70
Wed. 80
Thanks for any help you can provide.