A shopping mall charges $30 per vehicle plus $2 per person as an admission fee. The total charge for a vehicle with x people is f(x) = 2x +30. How will the graph of this function change if the per vehicle charge is changed to $10 per vehicle? The line will shift vertically down by $10. The line will shift vertically up by $20. The line will shift vertically up by $10. The line will shift vertically down by $20.