$41.$ If E is the duration, ES and EF are die earliest start and finish times, LS and LF are latest start and finish times, then the following relation holds goodEF$=$ES$+$DLS$=$LF$-$DLF $=$ LS $+$ DD $=$ EF$-$ESall of the above$\mathrm{.}42.$ If TL is the largest allowable event occurrence time, total activity slack $($s$)$ is equal tolatest start time earliest start timelatest finish time earliest finish time $($EFT$)$TL$-$EFTall of the abovenone of the above$\mathrm{.}43.$ In a PERT chartall activities should be numberedonly important activities should be numberedonly critical activities are numberedonly selected activities are numberedno activity is numbered.