Some spacecraft design uses a solar sail made of aluminized plastic. As sunlight reflects off the sail, radiation pressure drives the spacecraft outward away from the sun.

a. If the sail material has a density of 600.0 kg/m3, what is the maximum thickness of the sail for which the force due to radiation pressure exceeds the gravitational force on the sail?

I was thinking the equation to use is 2I/C = G(M1M2)/r but I'm not sure how to work this out. The distance between the sun and the sail isn't given but I'm assuming it'll get canceled out. How do I even find the thickness of the sail if I'm only given the density?

b. If the collector's area is 2.2e6 m^2. its thickness is 1 μm, and the craft carries a 99.0 kg payload, what is its acceleration at the radius of the Earth's orbit?