First he should consider a business that maximizes profits and minimises costs. So he can decide to invest in the stock market buy shares say safaricom and once the market is good he can sell the shares and also earn dividends so hell have tripled his profit. Say one share costs 1.89ksh so for 15000/1.89=7936.5 shares after a month he sells at 5.60ksh hell have 5.60*7936.5= 44,444ksh so hell have doubled the amount