A subcontractor that is scheduled to work on a critical project task originally quoted a cost of $5000 with a duration of 9 days. Eager to speed up the project, you requested a quote for the fastest the subcontractor could complete the tack. The subcontractor has just replied with a "fastest quote for the project task of 5 days for a cost of $7800. Assuming a linear relationship between the cost and duration of the original quote and the "fastest quote, what would you expect the tack to cost if you wanted it completed in 7days?