Correct Option: D

We know that,

Pt = Pc		1 +	μ2
			2

where, P_t= P_c + P_USB = 1000 + 200 + 200 = 1400 W P_c = 1000 W
Now,

1400 = 1000		1 +	μ2
			2

or	μ2	= 0.4
	2

or   μ² = 0.8
or   μ = 0.894
or   μ = 89.4%