1. (24 g)/(8 oz) = 3 g/oz
2. $2.00/(16 floz) = $0.125/floz
3. $4.50/lb × 3 lb = $13.50
4. A calculator or spreadsheet can process the list of numbers nicely. The unit rates I get are (per pound) $0.81, $0.90, $0.78, $0.85. So the lowest unit price seems to be ...
... 24 lb for $18.72 . . . . . . not the same as your choice