Correct order of heart conduction

SA node $\to$bundle of his $\to$ AV node  $\to$ Purkinje fibres $\to$ Ventricular syncytium

SA node  $\to$ AV node $\to$ bundle of his $\to$Purkinje fibres $\to$Ventricular syncytium 

AV node $\to$ bundle of his  $\to$SA node $\to$ Purkinje fibres $\to$ Ventricular syncytium 

Ventricular syncytium $\to$ SA node $\to$ AV node $\to$ Purkinje fibres $\to$ bundle of his