Sue must make estimated tax payments of $4,000 for the tax year. She makes the following payments:

Ist Payment.credit of $1,000 from her previous year refund

2nd Payment. $500 on April 20th

3rd Payment - $500 on May 31st

4th Payment - $1,000 on August 15th

5th Payment - $500 on October 15th

6th Payment - $500 on December 30th

Which of the following statements is true?

i. She has not made timely payments because her 2nd and 3rd payments were not made by April 15th

ii. She has not made timely payments because her 4th payment was not made by June 15th

iii. She has made timely estimated payments

iv. She has not made any timely payments because none of the payments were made by the required IRS schedule