You are considering purchasing a put option on a stock with a current price of $18. The exercise price is $20, and the price of the corresponding call option is $2.85. According to the put-call parity theorem, if the risk-free rate of interest is 3% and there are 90 days until expiration, the value of the put should be ____________.

A) $2.85

B) $4.70

C) $4.84

D) $6.31