Write a function that solves an algebraic expression given as a string. 

* The expression can include only sums and products. 

* The numbers in the expression are in standard notation (NOT scientific).

* In contrast, the function should return a string with the calculated value given in scientific notation with 5 decimal digits. 

# Example:
```python
strexpression = "5 * 4 + 6"
sum_prod(strexpression) = "2.60000e+01"
```