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Learnability has decreased in some respects compared to design A. The user may not know that they can specify multiple objects in each frame.They could learn by accident, or by watching someone else do it. Regardless, we could improve on this by having an object counter in the annotation view. We could also add certain affordances, like animations drawing sample figures around objects. Otherwise, the learnability is similar to or better than Design A because they don't have to select multiple objects from a grid.
Safety
Design C
Rather than take a picture of the bike, she simply takes a picture of it’s barcode. This does not require any annotation. 
Once Sally has taken pictures of each barcode, she can compare them in a table by price, reviews, warranty, etc. Since the software can determine that bikes are being compared (based on the product classification of each bar code), it can also provide additional values that can be compared on, such as construction materials (e.g. tire type). Sally is most interested in comparing the warranties for each bicycle, so she taps that: 
...And is taken to a table where each bike she imaged is compared.
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