Figure 3 shows a graph and a table of electric field strength against distance, ddd, from a charged sphere.

| Distance d d\,d in cm | Electric field strength in N/C |
|---|---|
| 2.0 | 36000 |
| 3.0 | 16000 |
| 4.0 | 9000 |
| 6.0 | 4000 |
| 8.0 | 2250 |
The equation relating electric field strength to distance, ddd, is
electric field strength=kd2 \text{electric field strength} = \frac{k}{d^2} electric field strength=d2kwhere k k\,k is a constant.
Using data from Figure 3, calculate the value of k k\,k when d=3.0d = 3.0d=3.0 cm.