A rectangle, presumably, as the cross section is going to be whatever shape the outward faces are (in the case of a vertical cross section like this one)
So as the path adds an extra 2 feet to each side I would start this by adding two feet to each part (so 25+2 x 38+2) which leaves you with 27ft by 40ft. Multiply to find this total area, which results in 1080. Now, you want to remove the actual area of the garden itself as this is not part of the path. So 25x38=950. Subtract 1080 by 950. This gives you just the area of the gardens path which would be 
For number 1, the median is 8
For number 2, the mode is C.100
And for number 3, the mean is D.410