SOLVE

LATER

Vanya and Students again !

Problem

Editorial

Analytics

Vanya has to now choose some Students from her class to go to the International Mathematical Olympiad. She knows for each student of her class, $$3$$ pieces of information about them, i.e. their 'Name', 'Age' and 'Aptitude'.

Vanya, to make work easier for her, and more difficult for you, defines the **Winning Quotient** of the Students choosen for the Olympiad from her class to be the Summation of their Aptitude Levels. In short, assume Vanya chooses Students $$x$$, $$y$$ and $$z$$. She considers the **Winning Quotient** to be Aptitude Level(x) + Aptitude Level(y) +Aptitude Level(z) in case of such a selection.

Now, considering that Vanya randomly chooses any arbitrary subset of Students from her class to visit the Olympiad, where the size of this subset has to be at least $$1$$, and the probability of each subset being choosen is equal, Vanya wishes to know the Expected Value of the **Winning Quotient** of the choosen Students.

She finds this task rather challenging, and wants you to help her out. Can you do it ?

Table : Students

Field | Type |
---|---|

Name | text |

ID | text |

Aptitude | int |

Round down your answer to **2** decimal places, and then select it to output.

**Sample Students Table** :

Name | ID | Aptitude |
---|---|---|

Micro | 12abcd | 1 |

Vanya | 13abcd | 2 |

Rhezo | 14abcd | 3 |

**Output**

Answer |
---|

3.43 |

**Input Constraints** :

The input table shall consist of no more than 10 rows. The Aptitude level of each student shall lie in the range from $$1$$ to $$10$$ inclusive. The Name and ID of each Student shall consist of at least 1 and no more than 10 characters.

Time Limit:
5 sec(s)
for each input file.

Memory Limit:
256 MB

Source Limit:
1024 KB

Marking Scheme:
Marks are awarded when all the testcases pass.

Allowed Languages:
MySQL,
PostgreSQL,
MSSQL,
Oracle_Db

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