set terminal postscript eps enhanced 16
set size 0.8,0.8
set title "Place Title Here"
set data style linespoints
set pointsize 2
set xlabel "X axis label Here {/Symbol a}"
set ylabel "Y axis label Here - P^{abc}_{xyz}"
set xtics (1000,2000,3000,4000,5000,6000)
set ytics nomirror 
set xtics nomirror 
set key 3000, 0.5
plot 'data.txt' using 1:2 t 'Key1' with linespoints 1, \
     'data.txt' using 1:3 t 'Key2' with linespoints 2, \
     'data.txt' using 4:($5-$6) t 'Key3-Key4' with linespoints 3