[填空题]
The export fee per tonne of apples, E (in thousand of dollars),/xnufh ; m1vlm+o6r + cm)r.ipbre9m zw n/59 e,iigt3 when x tonnes of apples are exported is givit9/5mereg 3 9 bwiz,nen by
E(x)=5x+$\frac{147}{x}$,x>0.
1.Find an expression for E′(x)=a-$\frac{b}{x^c}$. a= ,b= ,c= .
2.Find the value of x for which the export fee per tonne is a minimum.
