The Fastest Multiple

"We would definitely have a problem", Jame's boss said when he discovered he was poor with arithmetic. You have just one last chance to prove yourself right, his boss continued. At this time, James knew he had his balls on the line. How could i......Come fix this up!... his boss shouted before he could conclude his thinking. If $(2*2*2*2)=$8, what arithmetical model can i generate if i have $5*$5$5*$5$5*$5*$5?????. James is still chewing his pen cover... what model could bail James out???