Answer:
Explanation:
Given
Each student exert a force of 
Let mass of car be m
there are 18 students who lifts the car
Total force by 18 students 
therefore weight of car 
mass of car 

(b)
Cumulus and cumulonimbus<span />
Answer:
A -Added when in the same direction
Subtracted when in opposite directions.
Explanation:
Are there options? because there is 2 things im thinking of