A tank of water was drained at a constant rate. The table shows the number of gallons of water left in the tank after being drained for two amounts of time.

table: | draining time | water in tank |
| 10 | 450
——————————————— |
| 30 | 330
——————————————— |

a. What is the rate at which the water was drained from the tank?
b. How much water was in the tank before it started draining?
c. How long will it take fir the tank to drain completely?