Question 2
The terms of an arithmetic sequence add to $715.$ The first term of the sequence is increased by $1,$ the second term is increased by $3,$ the third term is increased by $5,$ and in general, the $k$th term is increased by the $k$th odd positive integer. The terms of the new sequence add to $836.$ Find the sum of the first, last, and middle terms of the original sequence.