An insurance company has six centres that process claims

An insurance company has six centres that process claims from customers. Each of the centres has been asked to measure its productivity in terms of the number of claims processed per employee per hour. The results are as follows. Centre A = 2.1 claims / employee / hour, Centre B = 1.6 claims / employee / hour, Centre C = 2.4 claims / employee / hour, Centre D = 4.5 claims / employee / hour, Centre E = 3.5 claims / employee / hour, Centre F = 3.4 claims / employee / hour. The publication of these figures causes much argument between the centre managers.
The managers of Centres B and F in particular point out that they process more different types of claim than the other centres. The operations vice president of the company accepts this point as perhaps explaining the differences in productivity. Centres A, D and E all process three types of claim, Centres C and F process six types of claim, while centre B processes nine types of claim.
(a) Which centres appear to be the most ‘efficient’?
(b) What advice would you give the operations vice president regarding the performance of the centres?