/* Matrix Vector Multiplication
 
Write a C program that multiplies a 2x2 matrix A with a 2x1 column vector x. 
The result is a 2x1 column vector b.
 
The relevant formulas for calculating the two components of b are shown below.
 
 
 Ax = b  <==>  | a1  a2 | * | x1 | = | b1 |  <==>  b1 = a1*x1 + a2*x2
               | a3  a4 |   | x2 |   | b2 |        b2 = a3*x1 + a4*x2
 
 
In other words, write a C program that takes six values from the user, 
calculates two values (b1 and b2) according to the above formulas, 
and then prints the vector b on the screen.
 
The result vector must be printed in a separate function.
The vertical bars to the right of the result vector must be aligned.
 
You can assume that the user will only enter integer values in the range -99 to +99
such that the calculated values for b1 and b2 can be printed with three characters or less.


============= START OF SAMPLE RUN =======================
Please enter the four values of matrix A (a1 a2 a3 a4):
3 5 1 -1
Please enter the two values of vector x (x1, x2):
-3 1
Vector b, the product of A and x, is therefore:
|  -4 |
|  -4 |
=============  END OF SAMPLE RUN  =======================
 
 
 
============= START OF SAMPLE RUN =======================
Please enter the four values of matrix A (a1 a2 a3 a4):
-12 3 3 1
Please enter the two values of vector x (x1, x2):
3 -1
Vector b, the product of A and x, is therefore:
| -39 |
|   8 |
=============  END OF SAMPLE RUN  =======================
 
*/ 

#include <stdio.h>
#include <stdlib.h>

void printVector(int b1, int b2)
{
	printf("Vector b, the product of A and x, is therefore:\n");
	printf("| %3d |\n", b1);
	printf("| %3d |\n", b2);
}

int main(int argc, char* argv[])
{
	int a1, a2, a3, a4;
	int x1, x2;
	int b1, b2;

	printf("Please enter the four values of matrix A (a1 a2 a3 a4):\n");
	scanf("%d %d %d %d", &a1, &a2, &a3, &a4);
	printf("Please enter the two values of vector x (x1, x2):\n");
	scanf("%d %d", &x1, &x2);

	// calculate
	b1 = a1*x1 + a2*x2;
	b2 = a3*x1 + a4*x2;

	// print the result
	printVector(b1, b2);
	
	// system("pause");
	return 0;
}