12 Trees in a forest may be affected by one of two types of fungal disease, but not by both. The number of trees affected by disease \(\mathrm { A } , n _ { \mathrm { A } }\), can be modelled by the formula $$n _ { \mathrm { A } } = a \mathrm { e } ^ { 0.1 t }$$ where \(t\) is the time in years after 1 January 2017.
The number of trees affected by disease \(\mathrm { B } , n _ { \mathrm { B } }\), can be modelled by the formula $$n _ { \mathrm { B } } = b \mathrm { e } ^ { 0.2 t }$$ On 1 January 2017 a total of 290 trees were affected by a fungal disease.
On 1 January 2018 a total of 331 trees were affected by a fungal disease.
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1. Show that \(b = 90\), to the nearest integer, and find the value of \(a\).
   

   12	Estimate the total number of trees that will be affected by a fungal disease on 1 January 2020.
   	[1 mark]

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2. Find the year in which the number of trees affected by disease B will first exceed the number affected by disease A.
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3. Comment on the long-term accuracy of the model.