Actually the reference point where Mr Mundim quoted the 30 Million swing at 10% +/- is
at 2.60 Br Rl to US. At Average Br Rl of 4.00 equates to a whooping (4-2.6) /2.6 * 100% = 53%.
If it is direct proportional to 30 million/ 10% swing then that is equal to 150 million savings.