In postgresql using query

WITH RECURSIVE rel_rec AS (
    SELECT
            1 AS depth,
            *,
            ARRAY[lvl] AS child_path
        FROM types_of_work
        WHERE parent_id IS NULL AND project_id = 14

        UNION ALL
        SELECT
            nlevel(r.path) + 1,
            n.*,
            r.child_path || n.lvl
        FROM rel_rec AS r
        JOIN types_of_work AS n ON n.parent_id = r.tow_id
        WHERE r.project_id = 14
)
SELECT
    t0.tow_id,
    t0.project_id,
    t0.path,
    t0.child_path,
    t0.lvl,
    t0.parent_id,
    t0.depth,
    t2.tow_cost
FROM rel_rec t0
LEFT JOIN (
    SELECT
        tow_id,
        tow_cost,
        tow_cost_percent,
        tow_date_start,
        tow_date_finish
    FROM tows_contract
    WHERE contract_id = 10
) AS t2 ON t0.tow_id = t2.tow_id
ORDER BY t0.child_path, t0.lvl;

we get a table

How to add the calculated sum of the costs of all nested children to this table? An example of this sum is the CUMULATIVE_COST column.
The table presented is a tree system.
The depth column shows the nesting level
The parent_id column shows the tow_id of the parent entity