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A message signal given by

\[ m(t)=\left(\frac{1}{2}\right) \cos \omega_{1} t-\left(\frac{1}{2}\right) \sin \omega_{2} t \]

is amplitude-modulated with a carrier of frequency $\omega_{c}$ to generate

\[ s(t)=[1+m(t)] \cos \omega_{c} t \]

What is the power efficiency achieved by this modulation scheme ?

- $8.33 \%$
- $11.11 \%$
- $20 \%$
- $25 \%$