PROGRAMMING:Segmented calculation of residential water charges [1]
In order to encourage the residents to save water, the water company adopts the method of step pricing according to the water consumption, and the water fee paid by the residents is related to the monthly water consumption of $$x $$(ton): when $$x $$does not exceed $$15 $$ton, $$y = 4x / 3 $$; After exceeding, $$y = 2.5x $$- $$10.5 $$. Please write a program to calculate the water charge.
###Input format:
The input gives the nonnegative real number $$x $$in one line.
###Output format:
According to the following format, output the monthly water consumption and water fee in one line, which are accurate to 2 decimal places. Please note that there is a space to the left and right of the equal sign.
```
F (input monthly water consumption) = calculated water charge payable
```
###Input sample 1:
```in
nine point five
```
###Output sample 1:
```out
f(9.50) = 12.67
```
###Input sample 2:
```in
fifteen
```
###Output sample 2:
```out
f(15.00) = 20.00
```
###Input sample 3:
```in
twenty-one point three
```
###Output sample 3:
```out
f(21.30) = 42.75
```
answer：If there is no answer, please comment
###Input format:
The input gives the nonnegative real number $$x $$in one line.
###Output format:
According to the following format, output the monthly water consumption and water fee in one line, which are accurate to 2 decimal places. Please note that there is a space to the left and right of the equal sign.
```
F (input monthly water consumption) = calculated water charge payable
```
###Input sample 1:
```in
nine point five
```
###Output sample 1:
```out
f(9.50) = 12.67
```
###Input sample 2:
```in
fifteen
```
###Output sample 2:
```out
f(15.00) = 20.00
```
###Input sample 3:
```in
twenty-one point three
```
###Output sample 3:
```out
f(21.30) = 42.75
```
answer：If there is no answer, please comment