Question 10
Four lamps form a 2 × 2 array. R, Y, B and W mean red, yellow, blue and white. Initially the top row is R Y and the bottom row B W. In minute 1 the two rows exchange colours; in minute 2 the two columns exchange colours. Repeat these two actions alternately, once per minute. What are the colours at minute 60? Options list top row / bottom row.
