Help me in solving SQW46 problem

My issue

I want this answer to understand the problem.

My code

/* Write a query to do the following
- We need to output the following - 'lane_id', 'origin', 'destination', and compute 'profit' 
- Order by decreasing 'profitability' 
- 'profit' is the alias for the column which stores the values 'Revenue' - 'running_cost'
- 'running_cost' is computed as (cost_per_distance x distance)
- **Hint:** you will need to use join all the tables - 'Revenue', 'Truck' and 'Network' and apply relevant conditions
- **Hint:** This has to be computed only for the truck_type '' */
SELECT
  r.lane_id,
  n.origin,
  n.destination,
  r.revenue - (t.cost_per_distance * n.distance) AS profit
FROM
  Network n
  JOIN Truck t ON n.truck_id = t.truck_id
  JOIN Revenue r ON n.connection_id = r.lane_id
WHERE
  t.truck_type = 'Truck2'
ORDER BY
  profit DESC;





 




Learning course: Learn Data Analytics using SQL and Python
Problem Link: Case study - Logistics Practice Problem in Data Analytics using SQL and Python - CodeChef