The number of arrivals per minute at a bank located in the central business district of a large city was recorded over a period of 136 minutes. The numbers of arrivals per minute and the frequencies of them happening are shown below.

ARRIVALS FREQUENCY

0 14

1 31

2 47

3 29

4 10

5 5

What is the expected number of arrivals?

a.2.037

b.3.427

c.1.001

d.2.986

what is the standard deviation of arrivals?

a.1.215

b.0.089

c.1.981

d.3.165