<span>The function can be represented as
y = f(x) =px(q -x)
So from the coordinate (6, 0)
y = 0 and x = 6
Substituting into the equation we have
0 = 6p(q - 6)
0 = 6pq -36p
6pq = 36p
q = 36p/ 6p
q = 6</span>
since Poisson distribution parameter is not given so we have to estimate it from the sample data. The average number of of arrivals per minute at an ATM is