The following table shows the annual inputs of phosphorus to Lake Erie:

Source Matric Toms$/$ Yr

Lake Huron $945$

Land Drainage $2844$

Municipal waste $7914$

Industrial waste $857$

Total Sources $12560$

Outflow $1900$

Retained $0660$

a$.$ Convert the retained phosphorus to concentration in micrograms per liter, assuming that Lake

Erie contains $4\mathrm{.}8\backslash$times $1014$ L of water and that the average phosphorus retention time is $2\mathrm{.}60$ yr$.$