1. For an electromagnetic wave, the average intensity is related to the rms electric field by

$I = c\varepsilon_0 E_{\mathrm{rms}}^2$

So,

$E_{\mathrm{rms}} = \sqrt{\frac{I}{c\varepsilon_0}}$

2. Given:

$I = \frac{315}{\pi}\ \text{W/m}^2, \qquad \varepsilon_0 = 8.86\times 10^{-12}, \qquad c = 3\times 10^8$

Substitute:

$E_{\mathrm{rms}} = \sqrt{\frac{315/\pi}{(3\times 10^8)(8.86\times 10^{-12})}}$

3. First compute the denominator:

$c\varepsilon_0 = 3\times 10^8 \times 8.86\times 10^{-12} = 26.58\times 10^{-4} = 2.658\times 10^{-3}$

Thus,

$E_{\mathrm{rms}}^2 = \frac{315/\pi}{2.658\times 10^{-3}}$

4. Now,

$\frac{315}{\pi} \approx 100.27$

So,

$E_{\mathrm{rms}}^2 \approx \frac{100.27}{0.002658} \approx 37724$

Therefore,

$E_{\mathrm{rms}} \approx \sqrt{37724} \approx 194.2\ \text{V/m}$

5. Nearest integer:

$\boxed{194}$