The waiting time in hours between successive speeders

The waiting time, in hours, between successive speeders spotted by a radar unit is a continuous random variable with cumulative distribution function
F(x)=0, for x<0,
F(x)=1−e−8x, for ,x≥0
Find the probability of waiting less than 12 minutes between successive speeders
(a) using the cumulative distribution function of X;
(b) using the probability density function of X.