In case of communication system development, the plan of improvement contains: the initial cost is $$6$ M

additional annual cost of $$3000$ with lifetime $50$ years and i$=5\%.$

The annual worth of this plan is:

Select one:

a$.$ $$-331680$

b$.$ $$-3000$

c$.$ $$-328680$

d$.$ $$-28680$