Solid rectangular just implies that its a 3D object and not a plain rect drawn on paper but its area can be calulated just like any other plain rectangle.
For rectangular surface are, we simply need the 2 sides - length and breadth.
Surface area = area of 2 square faces + 4 rectangular faces.
There is nothing like height of a rectangle, you can put it on either face and the standing side becomes the height
In cyliner we have 2 circular faces + a rolled over part. To get the area od this rolled part we need the height.