Step 1: List the corners:
Intersect the bounding lines in pairs and keep only points that satisfy every constraint: $(1,0)$, $(10,0)$, $(2,4)$, $(0,4)$, $(0,1)$.
Step 2: Compare z values:
Make a table: $z=3,\,30,\,26,\,20,\,5$ in that order. The largest is 30 at $(10,0)$ and the smallest is 3 at $(1,0)$.
Step 3: Use the given relation:
Difference $=30-3=27=3\lambda$.
Step 4: Solve:
$\lambda=\frac{27}{3}=9$.
Final Answer:
The value of $\lambda$ is 9 (option C).
\[ \boxed{9} \]