Hello user. here is your answer..

Let the total of 10 students be x.

Mean =. Total/No. of observations

15.7 = x/10

Therefore, x = 157

Now, Atq..

A new observation 19 is added.

Therefore, Total becomes : 157+ 19

new Total= 176

One more observation is added.. so number of observations=11

Mean = 176/11

Mean= 16

Therefore, your answer will be (b) :16

Hope it helps ❤ ❤