Final answer:
Luther's Doberman puppy will weigh 15.45 lb. next week.
Step-by-step explanation:
If Luther's pet Doberman puppy's weight increases by 3% every week and it weighs 15 lb. this week, we can calculate its weight next week by multiplying its current weight by 1 plus the percentage increase (1 + 0.03). So next week, the puppy will weigh 15 lb. x 1.03 = 15.45 lb. Therefore, option A is the correct answer.