select
    destination_city
    ,transport_name
    ,round(avg(timestampdiff(day, order_date, delivery_date)),2) average_transport_duration
    ,sum(total_cost) total_transport_cost
from order_info o
join transport_detail t on o.transport_id = t.transport_id
join cost_data c on o.order_id = c.order_id
group by 1, 2
order by 1, 2