Read the following article and answer the question.

I got randomly selected at work to test my " signature " basically like mystery shopper but over the phone . Anyway I got 3/10 which is pretty bad . I even got to listen to my conversation which in my defense was at the end of a 10 hour straight shift of answering phones . I sounded half asleep I never realised just how slack and full of slang the Aussie accent is .

What may be the reason why they were so tired ?
They are not used to working such a long day .