In a city, the number of deaths in different age groups over the past year is as follows: Age 0-18: 20 deaths Age 19-40: 50 deaths Age 41 and above: 130 deaths If the total population is 50,000, what is the all-cause mortality rate per 1,000 population for the 19-40 age group? a. 0.25 b. 1.0 c. 0.5 d. 2.5