Please check this for me cause i'm missing a zero in my answer

If an average of 0.5 customers arrive per minute at a ticket counter, what is the probability that exactly 4 customers will arrive in a 5 minute span

a. 0.0534
b. 0.50
c. 0.68
d. 0.134

I got 0.534 which is just like a. w/o the 0 but rounded down would be b., I did it a couple times on my calculator and thats what i get