영어 현재 과거 시제 He felt that his office life was going to be

He felt [that his office life was going to be difficult].

에서 왜 is가 아니라 was가 쓰엿나요? 앞으로의 일이니깐 is going to가 맞지 않아요?

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과거에서 본 앞으로의 일 즉 과거미래이므로 was s going to가 맞습니다.