A European call option and put option on a non-dividend paying stock both have a strike price of $51 and an expiration date in 6 months. The put sells for $2.50 and the call sells for $2. The risk-free rate is 5% per annum for all maturities, and the current stock price is $48. 

(a) Explain in your own word what the "put-call parity" is. 

(b) Check whether the put-call parity holds. 

(c) If the put-call parity does not hold, describe step-by-step how an investor can take the advantage of this arbitrage opportunity to make a profit.