Avg PO4^3- []'s in the deep and surface ocn's are 2.11 and 0.71umolkg^-1. Calc the residence time of PO4^3- in the deep ocn considering the carbon budget(Figure below) Write the general equation, calculation and units.

------ represents a Box outline

Surface---------------------------------
[P]
------------/\--------------==----------
---------\/-----------------==----------
(arrows moving \/(sinking)
up and down through Jc = 5.0Gt/y
surface and deep)

v =4.6 m/y

deep------------==----------------------
----------------==----------------------
\/ (sinking)
Bc = 0.15Gt/y

sediments-------------------------------