[Exer4-1] Exercise 11 of Book {Devore2017B} P.108
An automobile service facility specializing in engine tune-ups knows that $45\%$ of all tune-ups are done on four-cylinder automobiles, $40\%$ on six-cylinder automobiles, and $15\%$ on eight-cylinder automobiles. Let $X=$ the number of cylinders on the next car to be tuned.
- (a) What is the pmf of $X$?
- (b) Draw both a line graph and a probability histogram for the pmf of part (a).
Remark. Here pmf stands for probability mass function.