Government expenditure, G, satisfies the differential equation
dG/dt = -0.05G
where G is measured in billions of dollars and time t is in years. The initial condition is G(0) = 500.
(a) Solve this equation to express G in terms of t.
(b) Find the value of (i) G when t = 6; (ii) t when G = 125. Round your answers to three significant figures.