Choose the correct statement and why?

a) Momentum of an object is calculated as p= m . a p=m*@, where m is its mass and a - its acceleration. b) Kinetic energy of an object is calculated as K=- m*v, where v is its speed and m is its mass. 2 c) Potential energy of a deformed spring that follows Hook's Law is calculated as Ek* X E = k . x . where "k" is the stiffness coefficient and "x" is the deformation of the spring. d) none of the above