Keith Johnson has $$100,000$invested in a $2-$stock portfolio. $$30,000$ is invested in Potts manufacturing and the remainder is invested in Stoh$$s Corporation. Potts$$ beta is $1\mathrm{.}60$ and Stohs$$ beta is $0\mathrm{.}60.$ What is the portfolio$$s beta?

a$.$

$0\mathrm{.}60$

b$.$

$0\mathrm{.}66$

c$.$

$0\mathrm{.}74$

d$.$

$0\mathrm{.}82$

e$.0\mathrm{.}90$