A short while ago I was asked to help someone with a three dimensional integration problem. Specifically, we have a fuction F(x,y) = 16 - x - y^2, and the requirement is, (a) determine the volume under a defined area, and (b) determine the surface area within the same limits. I have no problem with (a), it's a double integral of the function F, and the two sets of limits of integration are relatively easy to work out. However, with part (b) I just cannot remember what it is that you have to integrate. The limits of integration are ok; they are the same as in part (a). Can anyone here help? I recall doing this at uni, some 45 years ago, but haven't been able to locate my old text books.