Let

T₁ =  tension in the tight side,
T₂ =  tension in slack side,
V = velocity of belt
T_C = centrifugal tension

Now, we know that

The power transmitted by a belt is given by

P = ( T₁ - T₂ )v

Putting values from eqn. (i)

T_max = Maximum tension to which the belt can be subjected, thus eqn. (ii) can be written as

For maximum power we need to differentiate the equation (iii) w.r.t v and equate it to zero.

Hence, the correct option is (C).