Which of the following costs are variable? Cost 10,000 Units 30,000 Units 1. $30,000 $90,000 2. 30,000 180,000 3. 50,000 180,000 4. 75,000 75,000 Only 2 Only 3 O 1 and 3 Only 4 Only 1 1, 2, and 3 O 1 and 2