Step 1: Draught animals are traditional sources of farm power.
Step 2: Bullocks are commonly used for ploughing, carting, and other field operations.
Step 3: The power developed by a bullock depends on size, breed, health, and working condition.
Step 4: A medium size bullock can develop power approximately in the range:
\[
360-550W
\]
Step 5: Hence, the correct answer is:
\[
\boxed{360-550W}
\]