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The number of bacteria in a population, \(P\), at time \(t\) hours is modelled by the equation \(P = a \mathrm { e } ^ { k t }\), where \(a\) and \(k\) are constants. The graph of \(\ln P\) against \(t\), shown in the diagram, has gradient \(\frac { 1 } { 20 }\) and intersects the vertical axis at \(( 0,3 )\).
- State the value of \(k\) and find the value of \(a\) correct to 2 significant figures.
- Find the time taken for \(P\) to double. Give your answer correct to the nearest hour.
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