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7. A store is running a promotion during which customers have two options for payment. Option one is to pay 90% of the purchase price two months after the date of sale. Option two is to deduct x% from the purchase price and pay cash on the date of sale. Determine the value of x such that a customer should be indifferent between the two options when valuing them using an effective annual interest rate of 8%. 8. Assume a varying force of interest, (t)=2t+16, find the accumulation function, a(t)