At the beginning of the Han dynasty, every male commoner aged twenty-three was liable for conscription into the military. The minimum age for the military draft was reduced to twenty after Emperor Zhao's (r. 8774 BC) reign. Conscripted soldiers underwent one year of training and one year of service as non-professional soldiers. The year of training was served in one of three branches of the armed forces: infantry, cavalry or navy. The year of active service was served either on the frontier, in a king's court or under the Minister of the Guards in the capital. A small professional (paid) standing army was stationed near the capital.
What was the lowest age a soldier could be conscripted after the end of Emperor Zhao's tenure? (If the question is unanswerable, say "unanswerable")
twenty