They started at 453, then climbed 162, so now they are at:
453 + 162 = 615 feet.
They then cllmb another 207 feet to get to:
615 + 207 = 822 feet.
They then descend ( climb down) 285 feet.
822 - 285 = 537 feet.
Now they need to get back tot he original 453,
so they have to descend:
537 - 453 = 84 more feet.
The answer is C.