Can anyone help me with this problem?

a) The oil consumption rate satisfies the equation C(t) = C0e^rt, where C0 is the consumption rate at t=0 (the number of barrels per year) and r is a constant. If the consumption rate is C0 = 2.5x10^10 barrels per year in 1976 and r= 0.06 how long will it take before 2x10^12 barrels are used up?

b) As the fuel is almost used up, the prices will probably skyrocket and other sources of energy will be turned to. Let S(t) be the supply left at time t. Assume that S= ds/dt = - (alpha)S, where (alpha) is a constant. Find S(t).