The following revenue figures were taken from Rosemont Corporation's adjusted trial balance at the end of the following months (adjusting entries are performed monthly whereas closing entries are performed annually, on December 31)

March 31 (end of the first quarter) $140,000

September 30 (end of the third quarter) $450,000

December 31 (end of the fourth quarter). $680,000

Compute how much revenue the company earned from

a. April 1 through September 30

b. October 1 through December 31

c. April through December 31