The store bought a batch of socks of the same specification for sale. In order to avoid change, the store priced them at a profit of 40%. In fact, they charged the minimum integer yuan higher than "price * even number". As a result, it costs 5 yuan to buy 2 pairs of socks, 8 yuan to buy 3 pairs of socks, and 12 yuan to buy 5 pairs of socks. Knowing that the cost and profit of each pair of socks are integer points, find the cost of each pair of socks.
商店进了一批同样规格的袜子甩卖，为了避免找零，按40%的利润先定价，实际上收取高于"定价*双数"的最小整数元．结果买2双袜子需要5元，3双袜子需要8元，5双袜子需要12元，已知每双袜子的成本和利润都是整数分，求每双袜子的成本．
<result>1.7</result>