TITLE: Are monics and epics in the category of finite dimensional vector spaces actually injective and surjective linear transformations?
QUESTION [7 upvotes]: Consider the category of finite dimensional vector spaces with morphisms being linear transformations. 
Is it still true that monics and epics are actually injective and surjective linear maps, respectively? The converse is surely true since the category is concrete. 
I know this monics and epics are precisely the injective and surjective maps in the category of Sets and in the category of groups, but it is not necessarily true in the category of topological spaces, so I'm just curious if it is true or not in the category of f.d. vector spaces, and if so why?

REPLY [2 votes]: @TreverWilson's solution is spot on. I like to use rank-nullity whenever I get the chance to though.
Let $f:V\rightarrow W$ be monic. Seeking a contradiction, suppose $f$ is not injective so $\dim\ker f\neq0$. This gives an exact sequence 
$$
0\rightarrow\ker f\xrightarrow{i}V\xrightarrow{f}W
$$ 
That is, $i$ is injective so $\dim\ker i=0$. Moreover, $f\circ i=0=f\circ 0$ so $i=0$. Thus $\dim\mathrm{im}\,i=0$. Now, applying rank-nullity to $i$ gives
$$
\dim\ker f=\dim\ker i+\dim\mathrm{im}\,i=0+0=0
$$
a contradiction. Hence $f$ is injective.
Proving that $f$ epi implies $f$ surjective is similar using the exact sequence 
$$
V\xrightarrow{f}W\rightarrow\mathrm{cok}\,f\rightarrow 0
$$