a these are merely the differences of the two

Question

(a) These are merely the differences of the two prices. Consequently the mark to market losses are given by {Q₁ - Q₀,Q₂ - Q₀,Q₃ - Q₀,Q₄ - Q₀,Q₅ - Q₀}.

Certainly negative losses are gains.

(b) You just compute the interest accrued after multiplying by 1/360 for every day and

(c) Subsequently adding the gains and losses.