phenylthiocarbamide or ptc molecule tastes very bitter those who can taste it however about

Phenylthiocarbamide, or PTC, is a molecule that tastes very bitter to those who can taste it. However, about 30% of people cannot taste it, due to a recessive allele in their DNA. Assume that the proportion with this genetic trait is exactly 30%. A researcher administers PTC to 20 randomly selected subjects. Let X be the number of these subjects who are able to taste PTC (a) What is the probability distribution of X? (b) Calculate: (i) the mean and standard deviation of X. (ii) P( X > 6) (iii) P( 4 ≤ X ≤ 9)