Three miles a day should be the correct answer
To solve this divide the length and width of the photo by 2. Your new dimensions should be 3in x 4in.
The third option would be correct.
Hope this helps! ;)
Since the surface is the top part of a sphere centred on the origin, the directions of steepest descent are any vector originating from the origin (0,0).
At (5,5), the direction would be dictated by the line joining (5,5) and the origin (0,0), i.e. along <5,5> or equivalently along <1,1>.
You can also go through vector calculus to arrive at the same result.