XYZ Inc., a diversified conglomerate, is deciding whether to buy a copper mine. XYZ already owns some gold mines and has recently invested in the biotech industry. XYZs cost of capital is currently 10%. The following is a list of other companies for which market data are available.

Firm	Industry	# shares (in millions)	Price/share	Debt (book value in millions)	Beta Equity
A	Gold/Biotech	3	10	15	1
B	Copper	1	5	1	1.02
C	Copper	2	20	0	0.8
D	Copper	1.5	3	3	1.37

As a simplifying assumption you can set all debt betas equal to zero.

What opportunity cost of capital should XYZ use for evaluating whether to buy the copper mine? Use a risk free rate of 7% and a market risk premium (rm-rf) of 8%.