I want accurate answer with proper explanation show all your work please

Suppose a consulting firm has 900 clients, each generating, on average $12,000 per year in revenue. Further, currently, the firm has an operating margin of 25% and a blended labor cost per hour of $90. From this, derive the average number of labor hours expended on each client each year.

A. 100 hours.

B. 120 hours.

C. 150 hours.

D. 200 hours.

E. The answer cannot be generated from this data.

Note: Please show work, I would like to know how to do the problem.