What is the arbitrage opportunity when $9-$month forward price is out of line with spot price for asset providing dollar income $($asset price $=$$$50$; forward price$=$$$55$; income of $$4$ occurs at $5$ months; $5-$month and $9-$month interest rate are $4\%$ and $6\%$ per annum; maturity of forward contract $=9$ months$)?$