Szukanie napisów w strukturze tablicy

shit.cpp: In function ‘int srednia(pojazdy*, int)’:
shit.cpp:36:40: error: ‘marka’ was not declared in this scope
   36 |                 if (strcmp(p[i].marka, marka) == 0)

#include <iostream>
#include <vector>
#include <iomanip>
#include <cmath>

using namespace std;

struct vehicle {
	string brand;
	double price;
};

void show_me(const vector<vehicle> & item)
{
    if (item.empty()){cout << "\t\t\tthe base is empty := " << item.size() << "\n";}
    else
    {
        cout << "\t\t\tindex := " << item.size() << "\n";
        cout << "\n";
        for(const auto & el : item)
        {
            cout << right << setw(16) << el.brand << " " << right << setw(30)
            << right << setw(8) << setfill(' ')
            << setprecision(2) << fixed << el.price << ".zl" << "\n";
        }
    }
}

double average(const vector<vehicle> & item, const std::string & name)
{
	double sum{0};
	int counter{0};
    for(const auto & el : item)
    {
        if(el.brand == name)
        {
            sum += el.price;
            ++counter;
        }
    }
	return abs(sum/counter);

}
int main()
{
    vector<vehicle> item = {
        {"bolid", 60.21},
        {"automobil", 45.09},
        {"kareta", 47.10},
        {"kareta", 40.10},
        {"bolid", 88.00},
        {"bolid", 74.00}
    };

    show_me(item);
    double medium = average(item,"bolid");
    cout<<"\nfind \"bolid\" average := "<< medium << "\n";

    return 0;
}