Answer:
![k = (+) ma/d](https://img.qammunity.org/2021/formulas/physics/college/j7uoo2y73gh785j802p0xfpu0fv3aqdaz1.png)
Step-by-step explanation:
For this particular case, the spring constant value will be positive because the work is being done in the direction of gravity. When the spring pulls it back the value of spring constant will be in negative because of work done in direction against gravity. The K.E and P.E will be maximum at fastest acceleration and lowest acceleration respectively.