Hi, I need to help with this problem

The interval chain complex is the chain complex I defined by

0 if n > 1,

I_n = Z if n = 1

Z ⊕ Z if n = 0.

with the only nonzero boundary map given by n → (−n, n).

Show that a chain homotopy between two chain maps C → D is exactly the same

as a chain map C ⊗ I → D.

Thanks