I am trying to calculate the standard deviation of the array waiting_Time. But, i get the error “MethodError: objects of type Float64 are not callable”. What am I doing wrong?

Here is my code:

```
using Distributions
function simulation(l, m, s, n)
tables = 3n ### the total tables each waiter can serve
departure = zeros(tables)
waiting_Time = zeros(0)
sigma = 1 ### the std of waiting_Time; updated in our while loop
counter = 0.0
while (counter <= (1.96(sigma/.01))^2) ### while our confidence in the mean waiting timem is below 95%
counter = counter + 1
u = rand(1)
arrival = -(1/l)*log.(u[1]) ### generate our customer arrival
dine = rand(Normal(m,s), 1) ### generate the dinning time of our arrived customer
if (arrival >= minimum(departure))
wait = 0.0
departure[indmin(departure)] = arrival + dine[1]
push!(waiting_Time,wait)
else
wait = minimum(departure) - arrival
departure[indmin(departure)] = arrival + wait + dine[1]
push!(waiting_Time,wait)
end
if (length(waiting_Time) > tables)
println(waiting_Time)
for i in 1:length(waiting_Time)
println(typeof(waiting_Time[i]))
end
sigma = std(waiting_Time)
end
end
results = (mean(waiting_Time))
return results
end
```