20. Calculate the time taken to empty the container

A conical container is fully filled with petrol. The radius is 7.7 \(m\), and the height is 12 \(m\). If the container can release the petrol through its bottom at the rate of 20 cu. meter per minute, in how many minutes the container will be emptied. Round off your answer to the nearest minute.

 

Time taken to empty the container: