Answer:
d = 1, so 1 - 10 - 2*1 + 7 = 8 + 1 - 10 - 3*1 is true!
Search up heating curve chemistry: it should look somewhat like that lol :). But, the last interval should have a small slope, the middle interval a big slope, and the first interval: a medium slope.
The answer is A. 28.5 hope this helped!!!! :)