How to count total number of lines of all .txt files?

I’m trying to figure out how to get total number of lines from all .txt files. I think the problem is on the line 6 -> let $((total = total + count )). Anybody knows what’s to correct form of this?

#!/bin/bash
total=0
find /home -type f -name "*.txt" | while read -r FILE; do
          count=$(grep -c ^ < "$FILE")
           echo "$FILE has $count lines"
           let $((total = total + count ))
        done
        echo TOTAL LINES COUNTED:  $total

Thank you