Let N* be the total number of ranchers in Uruguay, and N(t) be the number of ranchers who have adopted an improved pasture technology there. Assume that the rate of adoption, , is proportional to both the number who have adopted the technology and the fraction of the ranchers who have not (and so are susceptible to conversion). Let a be the proportionality constant. a. Write down the differential equation modeling N(t).
b. According to Banks (1993), N* = 17000, N(0) = 170, a = 0.5 per year.

Determine how long it takes for the improved pasture technology to spread to 80% of the population of the ranchers.