A large koi pond is filled with a garden hose at a rate of 10 gallons per minute. After 5 minutes the pond has 475 gallons of water.

A large koi pond is filled with a garden hose at a rate of 10 gallons per minute. After 5 minutes the pond has 475 gallons of water. Find a linear equation that models the number of gallons y of water in the pond after t minutes.