$\"\"$

Air is being pumped into a spherical weather balloon.

Volume of the balloon is represented by $\"\"$ and its radius is $\"\"$ .

(a)

$\"\"$ is the rate of change of volume with respect to radius.

$\"\"$ is the rate of change of volume with respect to time.

Volume of the spherical balloon with radius $\"\"$ is given by $\"\"$ .

Differentiate on each side with respect to $\"\"$ .

$\"\"$

Substitute $\"\"$ in the above expression.

$\"\"$ .