NET
19 Who knows if he will be a wise man or a fool? Yet he will be master over all the fruit of my labor for which I worked so wisely on earth. This also is futile!
Darby
19 And who knoweth whether he will be a wise [man] or a fool? yet shall he have rule over all my labour at which I have laboured, and wherein I have been wise under the sun. This also is vanity.
KJV
19 And who knoweth whether he shall be a wise [man] or a fool? yet shall he have rule over all my labour wherein I have laboured, and wherein I have shewed myself wise under the sun. This [is] also vanity.