A rapid-response maintenance company serves its customers who are located in four industrial estates.
Estate A has15 customers and is located at grid reference (5,7).
Estate B has 20 customers and is located at grid reference(6,3).
Estate C has 15 customers and is located at grid reference (10,2) but these customers are twice as likelyto require service as the company's other customers.
Estate D has 10 customers and is located at grid reference(12,3).
At what grid reference should the company be looking to find a suitable location for its service centre?