Question 16
A shipping company offers three different sizes of shipping boxes: Size A: $12\text{ m}\times9\text{ m}\times6\text{ m}$; Size B: $15\text{ m}\times12\text{ m}\times8\text{ m}$; Size C: $18\text{ m}\times10\text{ m}\times9\text{ m}$. Suppose that the $r$ pieces of Size A have the same total volume as $s$ pieces of Size B, which also have the same total volume as $t$ pieces of Size C. What is the minimum value of $r+s+t$?