Having Trouble Applying Forumla to whole column

Hi there, me again, back with my 3 dependent drop downs!

Good news, I've got them all sorted! However, it seems that I have to go through each of the last 2 columns, and apply the formula so it is dependent on the choice from the first drop down menu in its corresponding cell..example, E8 choice is dependent on D8 choice which is dependent on C8 choice...surely there is a way to have that formula applied down the whole columns so I don't have to go down each cell in both columns?!

Or am I talking nonsense..

Any help is extremely appreciated!