I could cost you could cost he could cost we could cost you could cost they could cost
V-ing form
I could be costing you could be costing he could be costing we could be costing you could be costing they could be costing
Perfect
I could have cost you could have cost he could have cost we could have cost you could have cost they could have cost
V-ing perfect
I could have been costing you could have been costing he could have been costing we could have been costing you could have been costing they could have been costing
Negation
Simple form
I could not cost you could not cost he could not cost we could not cost you could not cost they could not cost
V-ing form
I could not be costing you could not be costing he could not be costing we could not be costing you could not be costing they could not be costing
Perfect
I could not have cost you could not have cost he could not have cost we could not have cost you could not have cost they could not have cost
V-ing perfect
I could not have been costing you could not have been costing he could not have been costing we could not have been costing you could not have been costing they could not have been costing
Interrogative form
Simple form
could I cost? could you cost? could he cost? could we cost? could you cost? could they cost?
V-ing form
could I be costing? could you be costing? could he be costing? could we be costing? could you be costing? could they be costing?
Perfect
could I have cost? could you have cost? could he have cost? could we have cost? could you have cost? could they have cost?
V-ing perfect
could I have been costing? could you have been costing? could he have been costing? could we have been costing? could you have been costing? could they have been costing?
Interro-negative form
Simple form
could I not cost? could you not cost? could he not cost? could we not cost? could you not cost? could they not cost?
V-ing form
could I not be costing? could you not be costing? could he not be costing? could we not be costing? could you not be costing? could they not be costing?
Perfect
could I not have cost? could you not have cost? could he not have cost? could we not have cost? could you not have cost? could they not have cost?
V-ing perfect
could I not have been costing? could you not have been costing? could he not have been costing? could we not have been costing? could you not have been costing? could they not have been costing?