Look at the table. make a conjecture about the sum of the first 15 positive even numbers.

Be observing the table, we can write the following conjecture:

When adding consecutive even numbers, starting from 2 to .

Then the sum is equal to: 


Then, the sum of the first 15 positive even numbers (which is the sum of 2 to 30) can be calculated with the previous conjecture by setting :


The answer is 240.

The correct answer will be d. -4