2.What … (will happen) to our sales if we … ( increase) our advertising costs by 5%?
2.What … ( happens) to our sales if we … ( increase) our advertising costs by 5%?
2.What … (would happen) to our sales if we … ( increased) our advertising costs by 5%?
2.What … (would have happened) to our sales if we … (had increased) our advertising costs by 5%?