# Need help to solve a summation till infinity problem

I need to solve a problem in SageMath:

```
P = sum of alpha_m from (K-1) till infinity,
```

where

```
alpha_m = integrate((((lmd*t)^m)/factorial(m))*b(t)*exp(-lmd*t), t,0,infinity),
```

and `lmd`

is a constant value.

How to feed this in SageMath? I tried to input as:

```
sum((integrate((((lmd*t)^m)/factorial(m))*b(t)*exp(-lmd*t), t,0,infinity)), m,K-1,infinity)
```

It shows error.

You should provide the whole code. In particular, how are

`b(t)`

and`lmd`

defined ?