Fix Cost Function

[ramarea]

The following functions returned a nameerr. Is it the return? who knows?

# This function calcuates the inventory costs per period
def calculateInventoryCosts(self):
    return INVENTORY_COST * self.inventory

def calculateOrderCosts(self,qty_cost):
    return self.num_orders_placed * ORDER_COST + self.qty_orders_placed * qty_cost

def calculateLostSaleCost(self, qty_price):
    return self.discarded_orders * qty_price * SALE_LOST_COST_MULT