A utility company charges each customer a fixed monthly fee plus a usage fee that depends on the number of kilowatt-hours (kWh) consumed.
| k (kWh) | C (dollars) |
|---|---|
| 300 | 54 |
| 700 | 94 |
The table above shows the cost C, in dollars, for two different monthly usages k. Which equation gives C in terms of k?