高职高专《实用英语教程》翻译第57页上海交通大学出版社

高职高专,电工电子技术（有关自流电路）的问题
现在有100W和15W两盏白炽灯,额定电压均为220V,它们在额定工作状态下的电阻各是多少?可否把它们串联起来接到380V电源上使用?

英语问题请问：
灵通英语高职高专读写译教程里有这样段句话：
Carolyn was a 24-year-old college graduate.She had a bright future ahead of her.However,she also faced the problem that many up-and-coming college graduates face today:student debt.Two-thirds of today’s college graduates finish school with student loans.The average of these student and federal loans is about 19,000 dollars.
这段话中的The average of these student and federal loans is about 19,000 dollars.这一句,我总觉得有问题,
首先：these student应该是students,因为前面说了3分之二的学生,所以这里应该是复数.
第二,这句话怎么理解都觉得有问题,课本把这句话翻译成：这些学生的平均负债和联邦贷款平均数额都是19000美元.这里就更费解了.
个人觉得这里应该是：the average of these students' loans is about 19000 dollars.
不知道这样理解是否正确,请大家多发表宝贵意见.