Subtract the old reading from the new reading
7143 - 6997 = 146
146 units in all
Note: The first one hundred units costs 24p each unit
the rest cost 16p per unit
100 + 46 = 146
100(24p) = 2400p
46(16p) = 736p
2400 + 736 = 3136p
cost: 3136p
hope this helps
