What is a lower bound for the price of a four-month call option on a non-dividend-paying stock

Question:

What is a lower bound for the price of a four-month call option on a non-dividend-paying stock when the stock price is $28, the is $25, and the risk-free interest rate is 8% per annum?
Strike Price
In finance, the strike price of an option is the fixed price at which the owner of the option can buy, or sell, the underlying security or commodity.