Final answer:
The most appropriate discount rate to use for RiverRocks' evaluation of the acquisition of Raft Adventures is Raft Adventures' own WACC of 15.5%, as it reflects the specific risks associated with Raft Adventures' cash flows.
Step-by-step explanation:
The appropriate discount rate for RiverRocks to use to evaluate the acquisition of Raft Adventures should reflect the risk of the cash flows of the business being acquired. Since Raft Adventures has a Weighted Average Cost of Capital (WACC) of 15.5%, which is likely to include a risk premium for its specific business risks, this would be the most suitable rate to use. RiverRocks' WACC of 11.3% may not adequately represent the risk associated with Raft Adventures' cash flows and, therefore, may not be the proper discount rate for this investment decision.
Using a combined average WACC of both companies would dilute the specific risk profile of Raft Adventures, which could lead to an inappropriate valuation. Furthermore, the risk-free rate would not account for the business risk inherent in Raft Adventures' cash flows, making it unsuitable for discounting purposes in this scenario.