This question is not particularly tricky as long as it is read carefully.

First, calculate the masses of the Star and the Exoplanet. Double the mass to find the star mass (M). To find the planet mass, multiply by 0.01/100 = 1x10^{-4}. Mass of Star: m_{1} = 2 x 2x10^{30} = 4x10^{30}kg Mass of Exoplanet: m_{2} = 1x10^{-4} x 2x10^{30} = 2x10^{26}kg

Notice that the distance was given in km. You must convert to metres as the equation will only give the correct answer if Standard Units (SI units) are used. Therefore:

r = 1.5x10^{11}m

Now all that's left to do it substitute into the equation:

F = Gm_{1}m_{2}/r^{2}

Where:G = Gravitational Constant (from data sheet) = 6.67x10^{-11} m^{3} kg^{-1} s^{-2}and m_{1}, m_{2} and r are as they are above.

F = ((6.67x10^{-11})(4x10^{30})(2x10^{26}))/((1.5x10^{11})^{2})

F = 2.372x10^{24}N__F = 2.4x10__^{24}__N__