A service club has a constant membership of 1,000. X new entrants are added each year at exact age 35. Withdrawals are either by death or by retirement. 40% of those who reach age 50 retire at that time and all others retire at age;65. Express each of the following in terms of population functions: ^^

(a) The number of annual entrants at age 35.

(b) The number of members who retire each year at age 50.

(c) The number of members who die each year.