#"a) "exp(x) = e^x = 1 + x + x^2/2 + x^3/6 + ...#
#t = 12, r = 0.045, P = 500#
#=> A = 500*e^(0.045*12) = 500*e^0.54#
#~~ 500*(1 + 0.54 + 0.54^2/2 + 0.54^3/6)#
#= 500*(1 + 0.54 + 0.1458 + 0.026244)#
#= 500*1.712044#
#= 856.022#
#"b) "A = 2P#
#=> 2P = P*e^(0.045*t)#
#=> 2 = e^(0.045*t)#
#=> ln(2) = 0.045*t#
#=> t = ln(2)/0.045 = 15.4" years"#