What would my limits of integration be and why would i choose them?

Ineed someone to me answer my question i have to have this done and knocked out

Find the equation of a line that is perpendicular to line g that contains (p, q). coordinate plane with line g that passes through the points negative 3 comma 6 and 0 comma 5 3x − y = 3p − q 3x + y = q − 3p x − y = p − q x + y = q − p

Awater tank holds 18000 gallons. how long will it take for the water level to reach 6000 gallons if the water is used at anaverage rate of 450 gallons per day