How do I set up a table with 2 parents.

I have a contract table:

Contract
pk_id (I)


A child table that lists spaces for the contract (like "office", "warehouse", "retail", etc...)

ContSpace
pk_id (I)
fk_space (I)
fk_contract (I)

A child table that lists tasks for the contract (like "Space plan", "permit drawings", etc...)

ContTask
pk_id (I)
fk_task (I)
fk_contract (I)

Now I need a table to hold the fee minimum for each space/task combination.

ContFee
pk_id (I)
fk_task (I)
fk_space (I)
fk_contract (I)
Minimum (N)
Fee (C)

Is that the correct way to do it? I seems like a PITA to keep the ContFee table matching the 2 parent tables. Everytime a record is added to the ContSpace table, a record for each of the ContTask records need to be added to the ContFee table.