A carrier is simultaneously modulated by two sine waves

A carrier is simultaneously modulated by two sine waves with modulation indices of 0.3 and 0.4; the total modulation index—

1. Is 1
2. Cannot be calculated unless the phase relations are known
3. Is 0.5
4. Is 0.7

Given μ₁ = 0.3 and μ₂ = 0.4
μ_T = √μ²₁ + μ₂2 = √(0·3)² + (0·4)² = √0·9 + 0·16
= √0·25
= 0·5