A rectangular prism is completely packed with 180 cubes of edge length fraction 1 over 3 inch, without any gap or overlap. Which of the following describes the volume of this rectangular prism?
A- 19 unit cubes and 9 smaller cubes of volume fraction 1 over 27 cubic inch each
B- 19 unit cubes and 27 smaller cubes of volume fraction 1 over 27 cubic inch each
C- 6 unit cubes and 6 smaller cubes of volume fraction 1 over 27 cubic inch each
D- 6 unit cubes and 18 smaller cubes of volume fraction 1 over 27 cubic inch each