What does this combination compute and on which result does it complete?
CompletableFuture<Integer> a = CompletableFuture.supplyAsync(() -> 2);
CompletableFuture<Integer> b = CompletableFuture.supplyAsync(() -> 3);
CompletableFuture<Integer> c =
a.thenCombine(b, (x, y) -> x * y);