if X is a continuous random variable defined as:

f(x) = {

1/16x + 1/4, -4 <= x <= 0

-1/16x + 14, 0 <= x <= 4

}

a) what is the 0.8 quantile?

b) 45th percentile?

I know the basic premise of the question, but being defined in 2 parts is what eludes me.