Chen Hua, Jianguo, Xiang Ming, and Jiayuan, four members of a community owners committee, sat at a square table (one on each side) and discussed the greening plan next to the gate of the community. The professions of the four people are different, and each person's profession is one of college teachers, software engineers, gardeners, or postmen. Known: Chen Hua is a software engineer, he is sitting on Jianguo's left hand; Xiang Ming is sitting on the right hand of a college teacher; Jiayuan, who is sitting across from Jianguo, is not a postman.
Based on the above information, which of the following can be derived?
Jianguo is a postman, Jiayuan is a gardener