The system keeps on returns :
Oops, try again.
calling compute_bill with a list containing 1 apple, 1 pear and 1
banana caused the following error: local variable 'stock' referenced
Please help me check the mistake in this code.
def compute_bill (food): total=0 for item in food: if stock[item]>0: total=total + prices[item] stock=stock[item]-1 return total