How much did the British offer to purchase Goa?

Although there weren't any attempts made by the British to annex Goa. They did position their soldiers in Goa from 1798-1799 and 1802-1813. Upon Portugal's request in assistance to protect the  possession from the Dutch and French attack. In the year 1839, the British offered to buy Goa for £500,000. The Portuguese refused of course.