Preterite tense of regular verbs (actions or states completed in the past)

yo form of comprar

compré (I bought)

tú form of comprar

compraste

Ud./él/ella form of comprar

compró

nosotros/as form of comprar

compramos

vosotros/as form of comprar

comprasteis

Uds./ellos/ellas form of comprar

compraron

yo form of vender

vendí (I sold)

tú form of vender

vendiste

ud./él/ella form of vender

vendió

nosotros/as form of vender

vendimos

vosotros/as form of vender

vendisteis

uds/ellos/ellas form of vender

vendieron

yo form of escribir

escribí (i wrote)

tú form of escribir

escribiste

ud./él/ella form of escribir

escribió

nosotros/as form of escribir

escribimos

vosotros/as form of escribir

escribisteis

uds./ellos/ellas form of escribir

escribieron

which verbs that have a stem change in the present tense are regular in the preterite? which still has a stem change?

-ar & -er verbs are regular

-ir verbs still have stem change