Assume that on average, only $1$ in $80$ calls made by a teleseller can he/she approaches a potential client. So
1.) what is the probability that a teleseller fails to approach any potential client in $1000$ calls made,and
2.) what is the least number of calls that a teleseller has to make in order to give a probability greater than 0.9 of approaching at least one potential client
I have tried to solve the first part with poisson but not sure whether Poisson model is suitable for this cases. For the second one, i have no idea how to get the number of calls