LONDON (Reuters) - British finance minister Sajid Javid wants to boost Britain's annual economic growth rate to 2.7%-2.8% after Britain leaves the European Union, around twice its current underlying rate, he said in an interview with the Financial Times."I hope that in five years from now, we've made really good progress towards dealing with the big economic challenges," he said. "And there's two sort of biggies - growth and productivity".