calculus question

suppose there are 57.7 million people in Poland now and let P(t) denote the population of Poland t years from now. Assume that the population of Poland declines by 2% per year.

(a) express the change of P(t) by a differential equation.
(b) find the exact solution to the differential equation in part (a). hence, determine how many years it will take for the population of Poland to fall below 50 million.
(c) find an approximate solution to the differential equation in part (a) using Euler's method with a step size of 2 years. hence, estimate how many years it will take for the population of Poland to fall below 50 million.
(d) suppose the differential equation in part (a) is modified to
dP/dt = k( 1+0.3 t^(1/3) ) P
where k is a constant, and the population of Poland is still 57.7 million and declines by 2% per year at present ( t=0 ). redo your calculation in part (c) to obtain the new answer.

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need steps and explanation briefly. thanks!!!!!