Lower bound for the price of stock

Question

Problem:

Consider a six-month call option on a non-dividend-paying stock with the current stock price of $70 and the strike price of $65.

Required:

Question: Assuming the risk-free interest rate is10% per annum, the lower bound for the price of this stock is:

• -$1.58
• +$5
• $5.25
• $8.17

Note: Show supporting computations in good form.