Avocado Corporation paid $3,000 in estimated tax payments for the calendar year ended December 31, 2018. The corporation has an actual tax liability of $4,000 for the year.

a.

If no extension is requested, when is the tax return due?

b.

If an extension of time to file is requested and approved, when is the tax return due?

c.

If an extension of time to file is requested and approved, when is the additional $1,000 of the 2018 tax due?