A double calligraphy by Egyptian artist Ahmed Mustafa became the most expensive work by an Arab artist on Tuesday, selling for $662,500 at a Christie's auction in Dubai and raising hopes of a recovery in the Middle East’s struggling art market. Mustafa’s "Remembrance and Gratitude" went under the hammer in a packed auction house that saw around three-quarters of the 166 lots sold for a total of $6.7 million...