Answer: An astute trader can make $ 41,666.66.
Explanation: You must first change
$ 1,000,000 per pounds, which would leave a total of £ 500,000. ($ 1,000,000 / 2.00 = £ 500,000;).
Secondly spend £ 500,000 to euros, obtaining € 600,000 (£ 500,000 x 1.20 = € 600,000;).
Thirdly, with euros, buying dollars again, obtaining $ 960,000 (€ 600,000 x 1.60 = $ 960,000), that is, an arbitrage loss of -40,000 in relation to the initial investment.
Finally you must return in the opposite direction:
$ 1,000,000 / 1.6 (€) / 1.2 (£) * 2 - $ 1,000,000 = $ 41,666.66 that is, an arbitrage profit.