Question 254948
by hand
40m^2/8m^2 by hand
9*(40/8+1/2)
9*(5.5)
$49.50
40m^2/20m^2 spray gun
9*(40/20+1)+ 5*(40/20+1)
(9+5)(40/20+1)
14*3=$42.00
49.5-42=$7.50 saved 
It will cost that much in time to go rent it and return it and if you don't return it quickly it will eat up any savings.
The painter should have her own painting tools.
But where are you going to get a painter for $9 an hour?