[填空题]
The export fee per t: sueha )zgt* lqb:y)w/k)bd4ur0sp 5o rpr7hib:;n9m nne of apples, E (in thousand of dollars), when x tonnes of apples are exported is gin:rbmp9i;h r7ven 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.
