For a European put on a non-dividend-paying stock, the lower bound is:

$$\max\left(0, Ke^{-rT} - S_0\right)$$

Here:

• $S_0 = 24$
• $K = 30$
• $r = 3\%$
• $T = 0.25$ years

Compute the present value of the strike:

$$30e^{-0.03\times0.25} = 30e^{-0.0075} \approx 29.78$$

So the lower bound is:

$$29.78 - 24 = 5.78$$

Therefore, the correct answer is $5.78.