1- The acceleration of the rock is solve using the formula:
y = vot + 0.5gt²
14.2 = 0 + 0.5 g (1.811)²
g = 8.659
The weight of the rock is the strength of the gravitation field on the surface of Xena, so:
F = mg
F = 3.3 (8.659) = 28.576 N
2-
Using the gravitational force formula:
F = G m₁ m₂ / r²
28.576 = 6.67 x 10 ⁻¹¹ (3.3) m₂ / 14.2²
m₂ = 2.618 x 10¹³ kg