$6.$ An existing Rs$10000$ portfolio has a beta of $1\mathrm{.}5.$ A new investment of Rs$5,000$ with a beta of $0\mathrm{.}75$ is added

to this portfolio. What is the new beta of the portfolio?

$($i$)1\mathrm{.}20$

$($ii$)1\mathrm{.}30$

$($iii$)1\mathrm{.}25$

$($iv$)1\mathrm{.}15$

$($v$)$ None