Answer:
Step-by-step explanation:
From the given data
we observed that the missile testing program
Y1 and Y2 are variable, they are also independent
We are aware that
have
distribution with 1 degree of freedom
and
has x^2 with 2 degree of freedom

Since we have to find the density formula

We use method of transformation

There inverse function is 
We derivate the fuction above with respect to u

Therefore,
