What are the coordinates of point b in the diagram?

(3.25, -2.5)

(4, -5)

(1, 3)

(2.5, 0)

 The co-ordinates of point B are (4, -5).

Step-by-step explanation:  We are given to find the co-ordinates of point B in the diagram.

From the diagram, we note that

the co-ordinates of point A and C are (1, 5) and (1.75, 2.5) respectively.

Also, the point C divides the line segment AB internally in the ratio 1 : 3.

We know that if a point P divides a line segment joining the points (a, b) and (c, d) internally in the ratio m : n, then the co-ordinates of the point P are

Here, (a, b) = (1, 5), m : n = 1 : 3  and  (c, d) = ?

Therefore, the co-ordinates of point C will be

Thus, the co-ordinates of point B are (4, -5).