That's what a personal assistant is for, to always be there when the boss wants her to be. And to do what he demands. This man wanted to relieve the tension - the assistant was at hand, without hesitation and took advantage of her. According to her cries and sighs conclude - this is the work she likes!
Apparently smart people say that as a woman gets older she starts to want sex just as much as any man wants it in the beginning. It is not clear who fucks whom and who gets more pleasure from this process - the young stud or the mature women.