For the following project, what is the expected duration for Activity D$?$

$\backslash$table$[[,$DAYS,$\backslash$table$[[$IMMEDIATE$],[$AREDECESSORS$]]],[$ACTIVITY$,a,m,b,-],[$A$,3,6,6,-],[$B$,5,8,11,$A$],[$C$,5,6,10,$A$],[$D$,1,2,6,$B$,$ C$],[$E$,7,11,15,$D$],[$F$,7,9,14,$D$],[$G$,6,8,10,$D$],[$H$,3,4,8,$F$,$ G$],[$I$,3,5,7,$E$,$ F$,$ H$]]$

a$.\frac{48}{6}$

b$.\frac{33}{6}$

c$.\frac{39}{6}$