  In this paper, we consider a class of transportation problems which arises in
sample surveys and other areas of statistics. The associated cost matrices of
these transportation problems are of special structure. We observe that the
optimality of North West corner solution holds for the general problem where
cost component is replaced by a convex function. We revisit assignment problem
and present a weighted version of K$\ddot{o}$nig-Egerv$\acute{a}$ry theorem and
Hungarian method. The weighted Hungarian method proposed in the paper can be
used for solving transportation problem.
