What is one of the main differences between a 401(k) and a roth 401(k)

Emily works as a painter. for each job, it takesher 30 minutes to prepare an interior wall ofa house before she paints and 2 minutes persquare yard to paint that will. the graph belowshows the total time it would take her to do a job,based on the total area of the wallhow long does it take her to do a job when she paints a wall with an area of 15 square yards?