Note that the line passes through the points (0,3) and (7,7)
So.....the slope if this line is [7 -3 ] / [7 - 0] = 4/7
And using the point (0,3) the equation of the line is
y = (4/7)x + 3
And when x = 1001
y = (4/7)(1001) + 3 = 573
So (1001, n) = (1001, 573)