Answer
$\infty$
Work Step by Step
$\int ^{\infty }_{a}f\left( x\right) dx=\lim _{N\rightarrow \infty }F\left( N\right) -F\left( a\right) \Rightarrow $
$\int ^{\infty }_{0.3}5x^{-0.4}dx=(\lim _{x\rightarrow \infty }\dfrac {5}{-0.4+1}\times x^{-0.4+1})-\dfrac {5}{-0.4+1}\times 0.3^{-0.4+1}= \infty $
