[caity]

This seems like a pretty basic question and I've tried to do it a thousand times and keep getting the strangest answers that just... make no sense.  So I was hoping someone would be able to explain to me how to do it.  It seems simple enough but I guess I am missing some very basic principle behind it.  It was a homework problem I faced this week and a quiz question later, so I think my teacher is particularly fond of it and I should understand how to do it for future tests.

Mercury poisoning is a debilitating disease that is often fatal.  If the amount of mercury in a polluted lake is 0.4 micrograms Hg/mL.  What is the total mass in kilograms of mercury in the lake?  (The lake has a suurface area of 100mi² and an average depth of 20 ft)

Simple right?  I cannot understand why my answers do not seem to work.

[kd.gns]

can you post how you are doing the problem so we can see where it is you are going wrong?

[Sam (NG)]

calculate the volume of the lake, being very careful about conversion of units from miles and feet into metres cubed and then litres. (remember that if you have square miles, you have to square the conversion factor to metres etc).