The ability to pay [depends] on the vower, the age [category] upon the subject of the vow, the arachin upon the subject of the erech, and the erech upon the time of the erech. The ability to pay [depends] upon the vower. How so? A poor man who vowed the erech of a rich man gives the erech of a poor man, and a rich man who vowed the erech of a poor man gives the erech of a rich man.