Explanation:

Let total numbers of workers = X

Officers = 15

Rest workers = X - 15

Total salary of rest workers = 85 * (X - 15)

Total salary = 95X.

Officer's total salary = 15 * 525 = Rs. 7875.

Now,

95X = 85 * (X - 15) + 7875

10X = - 1275 + 7875

10X = 6600

X = 660.

Total numeber of workers = 660

Hence, option 4 is the correct answer.