4. A put with an exercise price of 50 has a price of 6, and a call on the same stock with an exercise price of 60 has a price of 10. Both put and call have the same expiration date. On the same set of axes, draw the "profit"

diagram for

a. One put bought and one call bought.

b. Two puts bought and one call bought.

c. Three puts bought and one call bought.

d. All three lines cross each other for the same value of ST. Derive this value.