Declare array in header file

I'm trying to declare an array for a graph problem in class.  When I try and print the arrays I get an "expression must have class type" error.

#pragma once
#ifndef GRAPH_H
#define GRAPH_H
#include <list>
#include <vector>
#include <string>
#include <set>

class Graph {
private:
	static const int MAXIMUM = 20;
	int mileageGraph[MAXIMUM][MAXIMUM];  //compiles so long as I comment out my print function
	int costGraph[MAXIMUM][MAXIMUM];
	std::vector<std::string> vertex;
	//int labels[MAXIMUM];
	int manyVertices;

public:  //this is where the functions go

	Graph();
	void addVertex(const std::string value);
	int getMileage(int source, int destination);
	int getCost(int source, int destination);
	void addEdge(int source, int destination, int mileage, int cost);
	bool isEdge(int source, int destination) const;
	//void shortestPath(int source);
	int getID(std::string vertex);
	std::string getName(int vertexId);
	int size();
	void printDirectFlights();
};

#endif // !GRAPH_H

void Graph::printDirectFlights()
{
	cout << "Direct Flights" << endl;
	cout << left <<
		setw(10) << "Source" <<
		setw(15) << "Destination" <<
		setw(10) << "Mileage" <<
		setw(10) << "Price" << '\n';
	for (int i = 1; i < MAXIMUM; i++)
	{
		for (int j = 1; j < MAXIMUM; j++)
		{
			if (costGraph.isEdge(i, j))  //breaks
			{
				cout << left <<
					setw(10) << getName(i) <<
					setw(15) << getName(j) <<
					setw(10) << mileageGraph.getMileage(i, j) <<  //breaks
					setw(10) << costGraph.getCost(i, j) << '\n';  //breaks
			}
		}
	}
}

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