A protective put costs:

$$\text{Stock price} + \text{put premium}$$

We are given the call price and can use put-call parity for a non-dividend-paying stock:

$$C + Ke^{-rT} = P + S_0$$

Where:

• $C = 3.00$
• $S_0 = 20.00$
• $K = 20.00$
• $r = 4\%$
• $T = 0.5$

First compute the present value of the strike:

$$Ke^{-rT} = 20e^{-0.04 \times 0.5} \approx 19.60$$

Then solve for the put price:

$$P = C + Ke^{-rT} - S_0 = 3.00 + 19.60 - 20.00 = 2.60$$

Total initial cost of the protective put:

$$20.00 + 2.60 = 22.60$$

So the correct answer is $22.60.