A normalized signal $x(t)$ is a scaled sum of three cosine terms. The signal is amplitude$-$modulated by a system having a modulation index of $1\mathrm{.}0.$

$x(t)=K(2cos(t)+4cos(2t)+2cos(3t))$

Most nearly, what value of $K$ is required to obtain a normalized signal?

$0\mathrm{.}13$

$0\mathrm{.}25$

$0\mathrm{.}5$

$1$