Answer:
We can solve this question using the formula below-
The formula for sum of n terms is,
For 14 months the last term is 14 and its sum is,
Here a = 1 and d = 1
For 16 months the last term is 16 and its sum is,
Here a = 1 and d = 1
OR
We can also solve this using simple addition like-
1. For a 14 month period the last term in the sequence is 14 and the series sum is;
2. For a 16 month period, the last term is 16 and the series sum is;
3. For a 16 month period, the last term is 20 and the series sum is;