Events are generated by processes that are uniquely named a$,$ b$,$ c$,..$hich event causally precedes the event with a vector clock of $($a$5,$ c:$15,$ d:$8)?$ a$)($a:$5,$ b:$1.$ c$12,$ d:$7)$

b$)($c$8,$ d:$8)$

c$)($a:$4.$ c:$14,$ d:$9)$

d$)($a:$6,$ c:$16,$ d:$15,$ e:$0)$