How are productivity, gross productivity, net primary productivity and secondary productivity interrelated ?

Explanation

(a) Produtivity is the rate of prodution of biomass (amount of living matter).
(b) Gross primary (GPP) is total amount of organic food synthesiszed by the producers per unit area and per unit time.
(c) Net Primay Productivity (NPP) is the amount of biomass produced produced by the producers per unit area and per unit . It is GPP minus losses by way of respiration and decomposition.
so NPP is represented as GPP - R.
(c) Secondary Productivity is the rate of biomass production by the consumers of per unit area per unit time. On avearage it is 10% for all the consumers.