시원스쿨 아이엘츠/토플

안녕하세요! 105p중에서 2가지 질문이 있습니다!

1.  Overall, over the 40-year period, Nigeria's population is expected to rise and overtake Indonesia, whose population growth will gradually slow down.

-> Overall, during the 40-year period, Nigeria's population is expected to rise and overtake Indonesia, whose population growth will gradually slow down

기간을 의미하는 거라면 over을 during으로 바꿔 쓸 수 있는지요?

2. It is predicted that by the year 2030, both countries will have equal populations of around 310 million people.

-> It is predicted that by the year 2030, both countries will have the same populations of around 310 million people.

'같은'을 의미하는 거라면 equal을 the same으로 바꿔써도 괜찮은가요? 

3. Overall, over the 40-year period, Nigeria's population is expected to rise and overtake Indonesia, whose population growth will gradually slow down.

-> Overall, over the 40-year period, Nigeria's population is expected to rise and overtake that of Indonesia, whose population growth will gradually slow down.

나이지리아의 인구가 인도네시아의 인구를 앞지른다는 의미라면  Indonesia 앞에 인구를 의미하는 that of가 있어야 하지 않나 혼자 생각해보았는데요,

이 경우 생략이 된 이유가 있을까요??