f = "out.txt"
set term pdf color size 20cm,15cm
set output "out.pdf"
set ylabel "Minutes"
set xlabel "# Workflows"
set yrange [1:40]
set xrange [1:128]
set xtics (1,2,4,8,16,32,64,128)
set ytics 0, 1
set style line 1 lt 2 pt 1 lc rgbcolor "blue"
set style line 2 lt 2 pt 2 lc rgbcolor "orange"
set style line 3 lt 2 pt 3 lc rgbcolor "red"

set style increment user

set key out horiz center top

set log x

plot f using 1:2 with lp title "min", f using 1:3 with lp title "mean", f using 1:4 with lp title "max"