$\left(C_{6} H_{5}\right)_{3} \dot{C}>\left(C_{6} H_{5}\right)_{2} \dot{C} H>\left(C H_{3}\right)_{3} \dot{C}>\left(C H_{3}\right)_{2} \dot{C} H$

The stabilisation of first two is due to resonance and last two is due to inductive effect.