$(20$ pts$).$ Solve Problem $8\mathrm{.}1,$ parts $($a$)$ through $($c$)$ only.

$8\mathrm{.}1.$ Arrow diagrams. Draw the arrow diagram that represents each set of the following

conditions. Note that the symbol $"<mi>"</mi>$ means "precedes," but not necessarily "immedi$-$

ately precedes." $($Hint: Only one solution is possible for each arrow diagram; activity

letters are not in standard form.$)$

a$.DA$

$DA$

$b.$

$c.$

$A$

$D$