IMAT 2016 Q3 [Painted Tins]

Below is a picture of a biscuit tin with four identical sides. A set of these tins is to be made that are all distinguishable from each other by colour alone. The manufacturer will paint each of the four sides either red or blue. The top and bottom are not painted.

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What is the greatest number of different tins that can be made?

A. 6
B. 7
C. 8
D. 4
E. 5