Stock Z is currently selling for $120. You believe that, one year from now, Stock Z will sell for either $155 (up-state) or $85 (down-state). The yield on a 1-year risk-free zero coupon bond is...

Stock Z is currently selling for $120. You believe that, one year from now, Stock Z will sell for either $155 (up-state) or $85 (down-state). The yield on a 1-year risk-free zero coupon bond is currently 4%. You have a European put option with a 1-year expiration date and an exercise price of $115. What is this option's delta (Δ) ?