$25.$ A voltage waveform is shown below, please find its RMS voltage value. Choose the value that is closest to the answer.

$($a$)0\mathrm{.}50$ V

$($b$)1\mathrm{.}23$ V

$($c$)1\mathrm{.}37$ V

$($d$)1\mathrm{.}56$ V

$($e$)1\mathrm{.}68$ V