Answer
$0.4$.
Work Step by Step
We know that probability of the event F is $P(F)=\frac{\text{number of favourable outcomes}}{\text{number of all outcomes}}=\frac{n(F)}{n(S)}$.
Since we have $n(F)=4$ and $n(S)=10$, then
$P(F)=\dfrac{4}{10}=0.4$.
