p(x≥ 1)= 1-(6/ 125)= 1 19/ 125

2

p(x = 0)=( 1-(4/5))( 1-p)( 1-q)= 6/ 125

p(x=3)=(4/5)pq=24/ 125

P=2/5 q=3/5 or p=3/5 q=2/5.

∵p & gt； ∴p=3/5 q=2/5

three

a =(4/5)( 1-(3/5))( 1-(2/5))+( 1-(4/5))(3/5)( 1-(2/5))+( 1-(4/5))( 1-(3/5))(2/5)= 37/ 125

b =(4/5)(3/5)( 1-(2/5))+(4/5)(2/5)( 1-(3/5))+( 1-(4/5))(2/5)(3/5)= 58/ 125

X 0 1 2 3

p(6/ 125)(37/ 125)(58/ 125)(24/ 125)

EX=225/ 125=9/5