Ir (b) A model for the number N ofpeople in a sub-urban community who have heard a certain 1 eased rumour is N = P (1 ) where P is the total population ofthe community and d is the number of days that have elapsed since the rumour began. In a community of 2000 residents,how many days will elapse before 7'50 have heard the rumour? [To the nearest whole number) (b) The number of years n for a piece of machinery to depreciate to a known salvage value can he lnslni ln(1 d) i is its initial value, and dis the annual rate of depreciation. found using the formula 11 = where s is the salvage value ofthe machinery, (i) How many years will it take for a piece of machinery to decline in value from $100000 to $10,000 ifthe annual rate of depreciation is [8 0/5)? (To 1 d. p)