Answer:
Time taken = 80 minutes.
Explanation:
The time it takes to deflate the air out of a spherical balloon is inversely proportional to the rate at which the air is released.
Let t be the time to deflate the air out of a spherical balloon and r be the rate at which the air is released.
We have

The balloon can be deflated in 70 minutes when the air is released at a rate of 400 cubic centimeters per minute.

We need to find how long will it take to deflate the balloon if the air is released at a rate of 350 cubic centimeters per minute

Dividing both equations

Time taken = 80 minutes.