SOLUTION
The mean is 4min
standard deviation is 1min
the z score is
where
then we have
The probability the call lasted less than 3 min will be
Therefore, the probability that (z < -1 ) is
[tex]\begin{gathered} Pr(z<-1)=Pr(0Hence, the percentage of the calls that lasted less than 3 min is 16%
There we have an information of two functions
Using this two functions , we need to find the composition of functions (h\circ g)(t).
The composition of two functions h and g is the new function , by performing g first and then performing h.
Composition of h and g (t) =
First plugin the value of
We know that , we need to find h(3t+3),
That is, to replace t by 3t+3,
Now distribute 2 into 3t+3,
Now plug in
Thus the solution is (D).