According to birth registration data available with the South Delhi Municipal Corporation,7 babies were born in a particular week in a private hospital. What is the probability that three babies were born on the same day of the week?

A

$$\frac{1800}{7^{5}}$$

B

$$\frac{1600}{7^{7}}$$

C

$$\frac{2100}{7^{7}}$$

D

$$\frac{2400}{7^{5}}$$