Sorrento, Inc. is considering adding leverage to its capital structure. Sorrento's managers believe they can add as much as $100 million in debt and exploit the benefits of the tax shield. However, they also recognize that higher debt increases the risk of financial distress. Based on simulations of the firm's future cash flows, the CFO has made the following estimates (all figures are in millions of dollars): Debt $0 $20 $40 $60 $80 $100 PV (interest tax shield) $0 $6 $12 $18 $24 $30 PV(financial distress costs) $0 $1.50 $2.80 $6.10 $9.70 $18.50 What is the optimal level of debt choice for Sorrento? $20 million $40 million $60 million O$ $80 million O $100 million