In a repeat of Hertz's experiment, a metal sheet reflects a wave and makes standing waves…

Step 1. The wavelength. Neighbouring nodes are $\lambda/2$ apart, so $\lambda = 2 \times 0.36\ \text{m} = 0.72\ \text{m}$.

Step 2. The frequency. $f = \dfrac{c}{\lambda} = \dfrac{3.00 \times 10^{8}\ \text{m/s}}{0.72\ \text{m}} = 417\ \text{MHz}$.

Step 3. The antenna. A half-wave antenna is $\dfrac{\lambda}{2} = 0.36$ m long, the same as the distance between the nodes.

Step 4. The power. The power is in proportion to $\omega^4$, hence to $f^4$. The factor is $1.5^4 = 5.06$.