These questions are from my AP chem assignment for this summer. Any help would be much appreciated! Thank you in advance!

first one..

"Mercury poisoning is a debilitating diesase that is often fatal. In the human body, mercury reacts with essential enzymes leading to irreversible inactivity of these enzymes. 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 surface area of 100 mi^2 and an average depth of 20 ft.)"

second one..

"The contents of one 20. lb bag of topsoil will cover 10. square feet of ground to a depth of 1.0 inch. How many bags are needed to cover a plot which measures 200. by 300. m to a depth of 2.0 cm?"

I fortunately have the answers to the problems! (They were odd numbered problems, meaning they were in the back of the book, haha.)

Answer to #1 is 7 x 10^5 kg

Answer to #2 is 1.0 x 10^5 bags

Unfortunately, I'm not getting these results when I try the problems. Lol.

If you could show me the calculations, that'd be great

Thanks againnnnn!