Final answer:
Caramels cost less per pound than pecan halves by $3.01.
Step-by-step explanation:
To determine which item costs less per pound, we need to calculate the cost per pound for each item.
For pecan halves, Marta spent $15.98 for 2 pounds, so the cost per pound is $15.98 / 2 = $7.99 per pound.
For caramels, Marta spent $22.41 for 4.5 pounds, so the cost per pound is $22.41 / 4.5 = $4.98 per pound.
Therefore, caramels cost less per pound than pecan halves by $7.99 - $4.98 = $3.01 per pound.