Answer:
I am assuming you are asking which is the cheaper option per ounce since you did not specify a question.
Option 1: 3.59$ for a 20 oz bag
3.59/20=.1795 $/oz
Option 2: 2.59 per 1 pound
1 pound = 16 oz
2.59/16= .161875 $/ozo
Since .16 dollars is less than .18 dollars, the second option, where 1 pound costs $2.59, is cheaper.