$.$ A wind farm operator wants to transmit $2500$ MW from a rural local to a load center located $300$ km away. Determine the number of three$-$phase, uncompensated transmission lines required to transmit this power with one line out of service $($this is to be stable under a n$-1$ contingency condition$)$ for the following options for line voltages: $($a$)345-$kV lines, Zc $=320,($b$)500-$kV lines, Zc $=275,($c$)765-$kV lines, Zc $=260.$ Assume that VS $=1\mathrm{.}0$ per unit, VR $=0\mathrm{.}95$ per unit, and max $=40$ deg, and a of $5000$ km