Activity $7$ is directly preceded by two activities$$activity $5$ and activity $6.$ Activity $5$ has an expected duration of five and an ES time of six. Activity $6$ has an expected duration of seven and an ES time of seven. Activity $7$ has an expected duration of $10.$ The ES for activity $7$ is:

Select one:

a$.$

$11$

b$.$

$14$

c$.$

$21$

d$.$

$24$

e$.$

$25$