PROGRAMMING:Four operations of real number

Please write four user-defined functions to return the sum, difference, product and quotient of two real numbers. The main function is to input two real numbers and call your custom function to output their sum, difference, product and quotient（ Please apply the function declaration in the program)
###Input example:
```in
5.0 2.0
```
###Output example:
```out
7.000000 3.000000 10.000000 2.500000
```






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