A new grain combine with a 20 year life can remove seven pounds of rocks from its harvest per hour. Any rocks left in the its output hopper will cause $35,000 damage in subsequent processes. Several investments are available to increase the rock-removal capacity, as listed in the table below. If the effective annual rate of return is 8%, what should be done? Note that the $35,000 damage is on an annual basis. For example, if nothing is done (1^st option), then there is a 20% chance of incurring $35,000 of damage each year.

Rock Removal Rate (RRR)	Probability of exceeding RRR	Required Investment
7 lb/hr	0.20	$0
8 lb/hr	0.10	$12,000
9 lb/hr	0.05	$18,000
10 lb/hr	0.025	$25,000