Geometry Basics · Superchallenge problem

A rectangle is cut into four smaller rectangles by one line parallel to its length and one line parallel to its width. The top-left piece has area $12$ cm$^2$, the top-right piece has area $18$ cm$^2$, and the bottom-left piece has area $30$ cm$^2$. What is the area of the whole rectangle, in cm$^2$?