East must respond with 4♠ !
It is the iconic weak pre-emptive response showing 6-10 HCP, 4 or more cards in the trump suit plus a singleton or void.

The response has two important objectives.
Firstly, although it is weak in High Card Points, its shape makes it ideal for producing at least two tricks by ruffing (trumping) in the hand's short suit (here ♦s). A Game contract is therefore usually secured even with 20 HCP or less in the combined hands.

Secondly the immediate jump response to the 4-level shuts out the Opponent from making any bid, which they otherwise well could have made with around 20 HCP in their combined hands themselves.

So is the Game contract possible with the above two hands ?
How many losers can West count ?