One year ago John Doe of USA invested in the stock of Lloyds, a U.K company. During the year, the stock declined by 20% but the British pound appreciated by 10%. If John Doe sold the stock

today his return would be ______.

a. 30%

b. -10%

c. -12%

d. 32%

e. None of the above.

answer is C, -12% but I want to know the formula and see the work to get there.