Question $7$

Lijuan has $$2,000$ dollars in GE$,$ $$4,000$ in Ford, and a loan of $$4,000$ from the bank at the risk free rate.

GE has a beta of $1\mathrm{.}1$ and Ford has a beta of $1\mathrm{.}4.$ Calculate the beta of Lijuan$$s portfolio.

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

$($b$)0\mathrm{.}78$

$($c$)3\mathrm{.}90$

$($d$)1\mathrm{.}18$

I would like to have a detailed answer because i don't understand how to get to the correct answer!!!