Plotting a graph of $K_W$ versus temperature gives:
By drawing a smooth curve of best fit through the points, the
relevant temperatures can be read off the graph for the given
values of $K_W$. If you draw the graph for the entire temperature
range, it is difficult to read off accurate values in the required
range, which are all smaller than $10\times 10^{14}$. Plotting the
curve through the first three points allows us to read off accurate
values.