Hi

I am confused on what formulas to use when answering questions like these:

1. A sample of pond water contained 88.00 µg g−1 of dissolved oxygen gas. Calculate the amount in grams of dissolved oxygen in 4.00 L of pond water.

2. A desirable level of dissolved oxygen in river water is 8 ppm. A sample of river water is found to have less than this, with 5.60 ppm oxygen. If 1.40 µg of dissolved oxygen was actually present in the sample, calculate the mass of water tested.

If someone could help me or give me some steps to solve the problems that would be great. Please explain simply