If the sequence of letters is $\text{A, F, K, P, \_\_\_}$, what comes next?

Let's find the positional values of the given letters in the English alphabet:
* $\text{A}=1$
* $\text{F}=6$
* $\text{K}=11$
* $\text{P}=16$

Now, let's observe the pattern of differences between consecutive terms:

* $6-1=+5$
* $11-6=+5$
* $16-11=+5$

Following the same pattern, the next positional value will be:

$$16+5=21$$

The letter corresponding to the alphabetical position $21$ is $\text{U}$.