Counter Artillery Howitzers - after the update how many need to be combined to be a deterrent/effective? (Check details in post)

Ignore the integrity and health of the bunker, assume opposing team has decided to shell a given structure with 3x 150mm gun firing full tilt - (between 7 & 8 rounds a min for both Warden and Colonial), if all 3 guns are striking the same connected bunker piece, how many howitzers are effective to counter such?

1? 2? 3? 4?

Again, we're ignoring the health and integrity, the question is how many howitzers, firing back would be sufficient to counter the incoming artillery.

Thanks!