Countries and provinces (1) P90532

UN wants to store information about the organization of its member countries and the provinces that these contain, attached with their GDP (gross domestic product)

The information about a determined province is stored in the following struct:

    struct Province {
        string name;
        string capital;
        int population;
        int area;   
        double gdp;
    };

The information about a determined country is stored in the following struct:

    struct Country {
        string name;
        string capital;
        vector<Province> provs;
    };

The information about all the countries is stored in a vector of countries:

    typedef vector<Country> Countries;

Using the previous definitions, implement the function

    double gdp(const Countries& p, char c, double d);

that returns the sum of the gross domestic products of all the provinces with density stricty greater than @d@ of all the countries in @p@ that starts with the letter @c@.

Observation

You only need to submit the required classes; your main program will be ignored.

Strictly obey the type definitions of the statement.