Write a function that gives loss amount if the given amount has loss else return none.
def loss_amount(actual_cost,sale_amount): 
  if(sale_amount > actual_cost):
    amount = sale_amount - actual_cost
    return amount
  else:
    return None
<s>[INST]<<SYS>>Given a task and its code, generate test cases for the code.<</SYS>>Write a function that gives loss amount if the given amount has loss else return none.
def loss_amount(actual_cost,sale_amount): 
  if(sale_amount > actual_cost):
    amount = sale_amount - actual_cost
    return amount
  else:
    return None[/INST]assert loss_amount(1500,1200)==None
assert loss_amount(100,200)==100
assert loss_amount(2000,5000)==3000</s>