A guy wants to know if this data sample is closer to a simple linear model or to an exponential model.

The table below represents 4 machines. We want to know the cost in function of the age of the machine. So X:age and Y:maintenance cost

Age 1 | 1.7 | 2 | 2.25

cost 0.5| 0.6 | 1.2 | 2

Either linear

Y = B_0 + B_1X

or Exponential

Y = ae^{bx}

Any tips to get me started?