[8] Robinson Crusoe spends 7 hours a day harvesting potatoes and collecting aluminum cans that have washed up on his island. He can harvest 5 potatoes per hour and he can gather 7 aluminum cans per hour. His utility over aluminum cans and potatoes is captured by his utility function: U03, (1) = pza , where p is the number of potatoes that he eats per day and a is the number of aluminum cans that he collects per day. How many potatoes will he choose to eat per day