Answer:
a) 
b) 
c) 
d) 
And using the CDF we got:


And using the CDF and the complement rule we got:

So then the probability required would be:
P(X < 60 or X > 80) = 0.25+0.333= 0.583
Step-by-step explanation:
For this case we define the random variable of interest X, and we know the distribution given by:

The density function is given by:

And the cumulative distribution function is given by:

Part a
We want this probability:

And we can find this probability with this difference:

And replacing we got:

Part b
We want this probability:

And using the CDF we got:

Part c
We want this probability:

And using the CDF and the complement rule we got:

Part d

And using the CDF we got:


And using the CDF and the complement rule we got:

So then the probability required would be:
P(X < 60 or X > 80) = 0.25+0.333= 0.583