I've been getting confused everytime we're graphing a summation with a continuous variable inside. For example, say I want to graph this equation with respect to $f$ ($y$ vertical, $f$ horizontal)
$$ y = 5\sum_{k=0}^\infty \operatorname{sinc}^2 \left(\frac k2 \right) \delta(f-k) $$
How do I account for the continuous variabality of $f$ inside? I know this maps to a comb function multiplied by varying constants, but I don't get how f is dealt with. Doesn't it vary continously with $k$?