Let the no. of service errors for Div. B = 'm'
and the total no. of customers for Div. B = 'n'
We need to find- m/n x 100

Statement (1) :
Total no. of Service errors for Div. A & B combined = 86+m
Total no. of csutomers for Div. A & B combined = 4850+n

Combined service error 1.5 = (86+m)/ (4850+n) x 100

We have two variables and one equation. INSUFFICIENT

Statement (2)
n = 9350
We still don't know 'm'. Hence, INSUFFICIENT

Combining (1) & (2)

Combined service error 1.5 = (86+m)/ (4850+9350) x 100

We can determine 'm' from above equation and subsequently calculate m/n x 100 for division B
The answer is (C)

This is the way I have interpreted the question

We need to get the service error rate for Division B

which will be ( E / N ) * 100
Where
E = number of service errors in B
N = total number of customers

Statement 1:
(E + 86 ) / (4850 + N ) = 1.5 / 100
= > 1.5 N - 100E = 1325
Since from statement 1 we can't get the ratio of E / N hence not sufficient

Statement 2:

Here we have the value of N but missing E hence can't be solved

But If we join statement 1 and 2 we can solve for the value of E and hence can get the result.

Hence IMO C