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**HallsofIvy** The first step is to take the logarithm of y and plot those points. If $\displaystyle y= Ce^{ax}$ then $\displaystyle log(y)= log(C)+ a log(e)x$, a straight line with slope a log(e) and y-intercept log(C). (The logarithm here is the common logarithm, base 10, since they tell you that log(e)= 0.4343)

The y value, where the line crosses the y-axis, is log(C) and so $\displaystyle C= 10^y$ for that y value. a is the slope of that line divided by log(e)= 0.4343. If this were exactly a straight line, you could calculate the slope using any two points but with inexact measurements, it is best to use the two points farthest apart: the slope would be $\displaystyle \frac{log(29.56)- log(6.59)/(4- 1)$.