For 6 miles every other day you really don't need a computer unless you're interested in tracking useless data.
If you start riding more days and miles for fitness and recreation, then look at a low cost bare bones computer that gives you trip distance, max speed, average speed, ride time, etc. You should be able to find one for under $20.
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The Lord is merciful and gracious, slow to anger and abounding in steadfast love. - Psalm 103:8
I am a cyclist. I am not the fastest or the fittest. But I will get to where I'm going with a smile on my face.