A rectangular prism is completely packed with 63 cubes of edge length fraction 1 over 3 inch, without any gap or overlap. Which of this best describes the volume of this rectangular prism? best answer a 2-unit cubes and 2 smaller cubes of volume fraction 1 over 27 cubic inch each

b 2-unit cubes and 9 smaller cubes of volume fraction 1 over 27 cubic inch each

c 4-unit cubes and 2 smaller cubes of volume fraction 1 over 27 cubic inch each

d 4-unit cubes and 3 smaller cubes of volume fraction 1 over 27 cubic inch each