Mary Green Decides to Take a Summer Course in London

Mary Green decides to take a summer course in London, England.Upon her departure from the Toronto airport Mary notes that the currency exchange rate is £1 = $1.60.Upon arrival in London, she finds that she can buy £1 for $1.65.Where should she have bought the pounds?  

A)  in Toronto, because Canadian dollars were cheaper 
B)  in Toronto, because pounds were cheaper 
C)  in London, because the value of the pound was higher 
D)  in London, because the value of the pound was lower