How to write a query with proportions to display statistics in MySQL?

Question

MySQL

Greetings! I can't figure out how to write a SQL query. There are initial data:

And you need to calculate the cost for each operator for each city, depending on how many applications from the total mass the operator has processed.

I calculate the cost per operator in each city as follows:
The number of operator applications in the city / the total number of applications in the city * the expense in this city

Answer 1

Something like this:

select
t3.user_id,
t4.city_id,
(t3.oper_zayavki / t4.`Заявки`) * t4.`Расход`
from Goroda_Statistika t4
inner join
(
  select 
  t1.user_id,
  t2.city_id,
  sum(t2.`Заявки`) as oper_zayavki
  from Operatory t1
  join Operatory_Statistika t2 on t2.user_id = t1.user_id
  group by t1.user_id, t2.city_id
) t3 on t3.city_id = t4.city_id

Answer 2

join three tables, group by user_id, city_id and correctly compose the result from aggregating functions