public class Account {
	private final int numberOfLines;
	private final double monthlyRate;
	private final double additionalLineRate;
	public Account(int numberOfLines, double monthlyRate, double additionalLineRate) {
		this.numberOfLines = numberOfLines;
		this.monthlyRate = monthlyRate;
		this.additionalLineRate = additionalLineRate;
	}
	public double computeBill() {
		return monthlyRate + (numberOfLines - 1) * additionalLineRate;
	}
}

public class AccountTest {
	private static final double GOLD_ADDITIONAL_LINE_RATE = 14.50;
	private static final double GOLD_MONTHLY_RATE = 49.95;
	private static final int ONE_LINE = 1;
	private static final int TWO_LINES = 2;
	private static final int THREE_LINES = 3;
	private static final double SILVER_MONTHLY_RATE = 29.95;
	private static final double SILVER_ADDITIONAL_LINE_RATE = 21.50;
	@Test
	public void goldAccounts() {
		assertEquals(49.95, goldAccountWith(ONE_LINE).computeBill());
		assertEquals(64.45, goldAccountWith(TWO_LINES).computeBill());
	}
	@Test
	public void silverAccounts() {
		assertEquals(29.95, silverAccountWith(ONE_LINE).computeBill());
		assertEquals(72.95, silverAccountWith(THREE_LINES).computeBill());
	}
	private Account silverAccountWith(int numberOfLines) {
		return new Account(numberOfLines, SILVER_MONTHLY_RATE, SILVER_ADDITIONAL_LINE_RATE);
	}
	private Account goldAccountWith(int numberOfLines) {
		return new Account(numberOfLines, GOLD_MONTHLY_RATE, GOLD_ADDITIONAL_LINE_RATE);
	}
}