I need detailed help with steps, not just an answer on how to solve, and where each number comes from :

Cummins Company budgeted $600,000 sales revenue for the first quarter of 2013, and a 5% volume increase for each of the following three quarters. The sales price per unit was set at $10, the manufacturing cost was expected to be $6, and company policy requires that each quarter's ending inventory consist of a quantity equal to 20% of the units budgeted to be sold during the following quarter.

Question : Contrary to the fact , assume that the corrected budgeted volume for the 2nd quarter was 80,000 units . Sales volume is expected to grow at 5% as before . Calculate the quantity of merchandise that was budgeted to be produced in the 3rd Quarter :

A) 80,800 B) 83,160 C) 84,000 D) 84,840 E) None