Exegesis:

kai [gar], if adopted, is best rendered as simple kai.

ean agathopoiēte ‘if you do good,’ cf. on v. 9. Here the meaning ‘to help’ is also adequate (cf. An American Translation).

Translation:

For even, preferably, ‘even,’ as in v. 34.

The same, or simply, ‘that’ in an emphatic position (Willibrord) or form (Tae’).

Quoted with permission from Reiling, J. and Swellengrebel, J.L. A Handbook on the Gospel of Luke. (UBS Handbook Series). New York: UBS, 1971. For this and other handbooks for translators see here . Make sure to also consult the Handbook on the Gospel of Mark for parallel or similar verses.