Given: A roof is served by 5 roof drains. the roof is 180` x 100`. rainfall is 4″ per hour. What is the size of a verticle roof drainage pipe if it drains the entire roof?

Given: A roof is served by 5 roof drains. the roof is 180` x 100`. rainfall is 4″ per hour. What is the size of a verticle roof drainage pipe if it drains the entire roof?