# Quiz - 10¶

Develop the function `cuantas_donas` that takes `n`, a positive integer, as a parameter, and returns a string in the form of `"Number of donuts: n"`, where `n` is the value passed to the function as an argument. However, if `n` >= 10, `cuantas_donas` will return `"many"` instead of `n`.

Examples:
`cuantas_donas(5)` -> `"Number of donuts: 5"`
`cuantas_donas(23)` -> `"Number of donuts: many"`

Develop the function `cadena_de_extremos` that, given a string `s`, returns a string with the first two and last two letters of `s`. However, if the string has less than 2 letters, it returns an empty string.

Examples:
`cadena_de_extremos("palmeras")` -> `"paas"`
`cadena_de_extremos("a")` -> `""`

Develop the function `remplazar_primer_caracter` that, given a string `s`, returns a string in which all occurrences of the first character in `s` are replaced by “*”, except for the first one. Note: use the method `.replace(value_to_replace, new_value)` to solve the exercise.

Examples:
`remplazar_primer_caracter("google")` -> `"goo*le"`
`remplazar_primer_caracter("dona")` -> `"dona"`

Develop the function `combinar_dos_cadenas` that takes two strings as arguments, `a` and `b`, and returns a new string in the following way:

• The new string has to be a combination of `a` and `b`.

• The new string will have the form `"<a> <b>"`, note the space between both.

• The new string will interchange the first two letters of `a` and `b`.

Suppose that `a` and `b` have more than 2 characters. For better clarification, see the following examples.

Examples:
`combinar_dos_cadenas("mix", "pod")` -> `"pox mid"`
`combinar_dos_cadenas("pezzy", "firm")` -> `"fizzy perm"`

Develop the function `es_palindromo` that takes a string `s` as parameter and checks if `s` is a palindrome or not, returning `True` or `False` accordingly.

Examples:
`es_palindromo("asa")` -> `True`
`es_palindromo("casa")` -> `False`

Develop the function `contar_ocurrencias` that takes two parameters: `frase` and `palabra`, both of type string. The function should return the number of times that `palabra` occurs in `frase`.

Examples:
`contar_ocurrencias("a ana y a mariana les gustan las manzanas", "ana")` -> `3`