Answer:
a)
, b)
, c)
, d) 
Step-by-step explanation:
a) The spring constant is calculated by using this expression:



b) The work needed to compress the spring from its initial position is:

![\Delta U_{k} = \frac{1}{2}\cdot (300\,\frac{N}{m} )\cdot [(-0.3\,m)^{2}-(0\,m)^{2}]](https://tex.z-dn.net/?f=%5CDelta%20U_%7Bk%7D%20%3D%20%5Cfrac%7B1%7D%7B2%7D%5Ccdot%20%28300%5C%2C%5Cfrac%7BN%7D%7Bm%7D%20%29%5Ccdot%20%5B%28-0.3%5C%2Cm%29%5E%7B2%7D-%280%5C%2Cm%29%5E%7B2%7D%5D)

c) The work needed to stretch the spring is:
![\Delta U_{k} = \frac{1}{2}\cdot (300\,\frac{N}{m} )\cdot [(0.2\,m)^{2}-(0\,m)^{2}]](https://tex.z-dn.net/?f=%5CDelta%20U_%7Bk%7D%20%3D%20%5Cfrac%7B1%7D%7B2%7D%5Ccdot%20%28300%5C%2C%5Cfrac%7BN%7D%7Bm%7D%20%29%5Ccdot%20%5B%280.2%5C%2Cm%29%5E%7B2%7D-%280%5C%2Cm%29%5E%7B2%7D%5D)

d) The work need to stretch the spring is:
![\Delta U_{k} = \frac{1}{2}\cdot (300\,\frac{N}{m} )\cdot [(0.2\,m)^{2}-(0.1\,m)^{2}]](https://tex.z-dn.net/?f=%5CDelta%20U_%7Bk%7D%20%3D%20%5Cfrac%7B1%7D%7B2%7D%5Ccdot%20%28300%5C%2C%5Cfrac%7BN%7D%7Bm%7D%20%29%5Ccdot%20%5B%280.2%5C%2Cm%29%5E%7B2%7D-%280.1%5C%2Cm%29%5E%7B2%7D%5D)

Answer: 4.00
Step-by-step explanation:
Total 52 students.
52 - 17 = 35 students left
35 - 5 = 30 students left
30 - 2 = 28 students left
Each class has 11 students that play ONE sport, which means 22 total in 2 classes. You're on your own now! It's not that hard, I'm sure you'll figure it out.