The cake weighed 5 130g.

The range of the guesses (5 040g, 5 060g, 5 110g, 5 120g and 5 150g) is 110 so the two 'wild' estimates must both be low or both high.

Since the difference between 5 040 and 5 060 is 20, 5 040 is 90 out and 5 060 is 70 out.