$\displaystyle \text{suppose we need to interview 150 blind men in a city(door to door survey).}$

$\displaystyle \text{the probability that a house is occupied is 0.73.}$

$\displaystyle \text{the probability that the house, if occupied, has at least one man is 0.90.}$

$\displaystyle \text{ the probability , given a man occupies the home, the man is blind is 0.15.}$

$\displaystyle \text{the likelihood that a blind man completes the interview is 0.95.}$

$\displaystyle \text{how many houses do we have to interview in order to have a 75\% chance}$

$\displaystyle \text{that we obtain 150 complete interviews from the blind men?}$

here's what I have attempted:

$\displaystyle \mbox{P(one complete interview is obtained from a house with a blind man)}\;=\; 0.73(0.90)(0.15)(0.95)=0.0937$

$\displaystyle \text{no of houses we would need to survey to complete 150 interviews} \;=\; \frac{150}{0.0937} = 1600$

now for the last part ,

$\displaystyle \text{With 75\% chance to obtain 150 interviews, we need,}\;1600 \times 0.75 \;=\;1200$

is this the right approach?