You are a physiologist on a space flight to a distant planet.

Please help! I have no idea on how to do this:
You are a physiologist on a space flight to a distant planet. You discover intelligent humanoid aliens inhabiting the planet, and they willingly submit to your tests. You discover that the alien’s kidney handles the sugar alcohol mannitol just like our kidneys handle inulin. You also test the alien for its renal handling of glucose. The data from that experiment are: Plasma level (constant over 24 hours): 6 g/dL of mannitol and 2 g/dL of glucose; 24 hour urine sample: volume of 2 L, containing 144 g mannitol and 52 g glucose. Answer each of the three questions below.
a. What is the alien’s GFR?
b. What is the alien’s clearance rate for glucose?
c. How does the alien handle glucose in relation to mannitol (filtered, reabsorbed, secreted)?