$$ Apple would like to determine their optimal capital structure and are considering two additional target structures of $2\mathrm{.}5\%$ debt and $97\mathrm{.}5\%$ equity or $10\%$ debt and $90\%$ equity. They plan to issue additional debt and repurchase shares.$$ a$.$ Determine Apple$$s unlevered beta $($bU$).$ b$.$ Re$-$lever their beta for each target capital structure and use the new betas to determine their new costs of equity for each target capital structure. c$.$ If they increase their debt to $2\mathrm{.}5\%$ of capital, the cost of debt will rise to $4\%.$ If they increase their debt to $10\%$ of capital, the cost of debt will rise to $5\%.$ d$.$ Calculate the new WACC for each target capital structure.$$ e$.$ Which is the optimal capital structure for Apple?$$ Why is this structure optimal? What do you recommend Apple should do with their capital structure?