P Corporation uses the calendar year as its tax year and the accrual method as its overall accounting method. S Corporation uses a fiscal year ending June 30 as its tax year and the cash method as its overall accounting method. On July 31, 2019, P acquires all of S's stock, and the P-S affiliated group elects to file a consolidated tax return for 2019.

a. What tax year must the group use in filing its consolidated tax return? 

b. What overall accounting method(s) can P and S Corporations use?

c. What tax returns must the corporations file?