Surface Area and Volume · Superchallenge problem

Stacks of $1$-cm cubes stand on a $3$ by $3$ square on the table, one stack on each square, all glued together. Looking down from above, the heights of the stacks are:

Back row: $3, 1, 2$

Middle row: $2, 2, 1$

Front row: $1, 3, 2$

What is the surface area of the whole solid, including the bottom, in square centimeters?