If you really want to know how much wrapping paper will be used, you have to give some specifications as to the amout of overlap in each of the three directions. On the other hand, if you just want to know the surface area of a rectangular prism, then you should say so.
A rectangular prism with dimensions , , and has 6 faces. The total surface area is the sum of the areas of the 6 faces. Two of the faces have area , two of them have area , and two of them have dimensions . Do the arithmetic.
John
My calculator said it, I believe it, that settles it