Suppose that the modulation signal is  mt=Amcos2πfmt and the carrier signal is xct=Accos2πfct. Which one of the following is conventional AM signal without over modulation

Conventional AM signal without over modulation means (μ<1) xt=(Ac+mt)cos2πfct ⇒xt=(Ac+Amcos2πfmt)cos2πfct ⇒xt=Accos2πfct+Amcos2πfmtcos2πfct Now comparing with option (3) xt=Accos2πfct+Ac4cos2πfmtcos2πfct We get, Am=Ac4 ⇒AmAc=14 ⇒μ=14  means under modulation