If it takes a planet 2.8 × 108 s to orbit a star with a mass of 6.2 × 1030 kg, what is the average distance between the planet and the star?
1.43 × 10^9 m
9.36 × 10^11 m
5.42 × 10^13 m
9.06 × 10^17 m

We can find the answer from formula for orbital velocity v=√{(G*M)/R}, where G is the gravitational constant and G=6.67*10^-11 m³ kg⁻¹ s⁻², M is the mass of the star and R is the distance from the planet to the star. Also, v=ωR, where ω is the angular velocity and R is the radius. 

ωR=√{(G*M)/R}, now, ω=2π/T, where T is the orbital period of the planet

(2π/T)*R=√{(G*M)/R}, we "put to the power of 2" both sides to get rid of the square root and get:

{(2π/T)*R}²=[√{(G*M)/R}]², 

(4π²/T²)*R²=(G*M)/R, we multiply by R:

(4π²/T²)*R³=G*M, now we solve for R and get:

R³=(G*M*T²)/4π², we take the third root to get R:

R=∛{(G*M*T²)/4π²}, plug in the numbers and get:

R=9.36*10^11 m 

And this is the average distance between the planet and the star. 

Iread this book last year so take this with a grain of salt.gene jumps from the tree to compete with finny due to the fact that gene is always trying to do better than finny. he is put under the grasp of peer pressure due to finny almost forcing him to do this. ever since he first jumped finny kept pressuring him to jump since he thought gene enjoyed jumping.rather than uses this answer you should probably just reread chapters 3-4