manabarb question

[TheRogue]

if my opponent let say declares there taping 4 mana and are going to use 3 to cast a 3 cost spell can they used the 4th to activate c.o.p. RED and prevent 4 damage from manabarbs.

since i'm under the impression manabarbs is triggered u end up with 4 triggers going on the stack.
does this count as 4 individual sources of red damage?

circle of protection say it stops the next red source that would deal you damage does this prevent all 4 points of damage from 1 manabarbs? Or does it need 4 mana to prevent all 4 triggers?

[A_Outcast]

each time they tap a land manabarb triggers and attempts to deal 1 damage to them.  so oif they tap 4 lands mana barb triggers 4 times dealing 1 damage each.  so he could only prevent 1 of the 4 damage.