题目内容：
C Co uses material B, which has a current market price of $0·80 per kg. In a linear program, where the objective is to maximise profit, the shadow price of material B is $2 per kg. The following statements have been made:
(i) Contribution will be increased by $2 for each additional kg of material B purchased at the current market price
(ii) The maximum price which should be paid for an additional kg of material B is $2
(iii) Contribution will be increased by $1·20 for each additional kg of material B purchased at the current market price
(iv) The maximum price which should be paid for an additional kg of material B is $2·80
Which of the above statements is/are correct?
A.(ii) only
B.(ii) and (iii)
C.(i) only
D.(i) and (iv)
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