You are planning for the defense of an island against invasion. The garrison on your island has 8000 soldiers, with a Lanchester aimed fire effectiveness of .1. The adversary will land an invasion force of 12,000 troops with an effectiveness (rho) of .05. Additionally, the attackers will be reinforced on or about day 5 with an additional 5,000 troops.

Reinforcing the island is not an option for blue, BUT the NCA and President are convinced that if the garrison can last until the 15th day, Diplomatic measures may end the conflict. The Navy has been tasked with delaying the arrival of the additional 5000. How much does the Navy need to delay the adversary's arrival in order to meet the President's goal?