Returns to scale - Constant Function

Suppose we have a production function $f(z)=2$.

I am asked to determine whether the function exhibits increasing, decreasing, constant or no returns to scale.

For $t>0$, $f(tz)=2$.

I'm not sure about the answer: should I say the function exhibits no returns to scale whatsoever or take different values for $t$ ($0<t<1 \implies$decreasing returns to scale, $t=1 \implies$ constant returns to scale, $t>1 \implies$ increasing returns to scale)?

• You want to find a relation between $tF(z)$ and $F(tz)$ for all $t > 1$ (or 0 for CRS). So since $2t = tF(z) > F(tz) = 2$ for all $t > 1$, we see decreasing returns to scale. Commented Nov 8, 2016 at 5:06
• @KitsuneCavalry If the question was good enough to upvote and answer, then the answer is good enough to post as an answer. Commented Nov 8, 2016 at 7:13

You want to find a relation between $tF(z)$ and $F(tz)$ for all $t>1$ (or $0$ for CRS).
So since $2t=tF(z)>F(tz)=2$ for all $t>1$, we see decreasing returns to scale.