$S/N$

c

$E\left[N\right]$

1

0

3.000000

2

5

1.898436

3

10

0.7320757

4

15

0.240542

5

20

0.072938

6

25

0.021071

7

30

0.005893

8

35

0.001610

9

40

0.000432

10

45

0.000115