Answer:
The value of 
Step-by-step explanation:
We have given 
d=1.7
We have to find 
So,
from the formula

When n=14




Using the formula:

When n=26
![s_{26}=\frac{26}{2}[2(-18)+(26-1)(1.7)]](https://tex.z-dn.net/?f=s_%7B26%7D%3D%5Cfrac%7B26%7D%7B2%7D%5B2%28-18%29%2B%2826-1%29%281.7%29%5D)
On simplification we get:

2.16 is greater. To do this start from the left and compare the numbers. For example, 2 is the same in both but 1 is greater than 0, so the answer is 2.16.
For Range you take the biggest number and subtract it with the smallest. So:
January = E14,000
Febuary = E9,000
March = E10,000
All Three Months = E17,000
Hope this helps,pleeease vote as brainliest!