In the two columns below, you find verb bases and imperfective forms for a number of verbs in Tagalog (Austronesian) (Schachter and Otanes 1972: $365)$ :
Write a rule that shows how the imperfective is formed in Tagalog.
Now consider these data:
$\begin{array}{ll}\text { b. Verb bose } & \text { Imperfective } \\ \text { lagyan } & \text { linalagyan } \\ \text { regaluhan } & \text { rineregaluhan } \\ \text { walisan } & \text { winawalisan }\end{array}$
Apparently the imperfective forms in (b) are less preferred, but possible, imperfective forms for the same verbs. Write an alternative rule that accounts for these forms.
Finally, what are the two imperfective forms that you might expect from the verb stem yapakan 'step on'?