According to a Wall Street Journal article "MCI, in New Phone War Skirmish, Files Suit over AT&T Ad Claims," MCI was upset with AT&T over allegedly false claims that AT&T's service is cheaper than MCI's. Suppose that the typical consumer is a small business, Woodbrook Electronics. Woodbrook uses MCI as their long-distance carrier and currently places 100 calls per month. MCI charges a price of $0.80 per phone call. Woodbrook used to subscribe to AT&T and placed 90 calls per month at AT&T's old rate of $.90 per phone call, but switched to MCI to take advantage of the lower price. Based on this data, estimate the equation for Woodbrook's demand assuming it is linear.