# 4.13.jl
# created on 2020-11-22
# $Id: 4.13.jl 1.1 2020/11/22 03:44:59 s Exp $

using Printf

# input
s_percent = [7.67, 8.27, 8.81, 9.31, 9.75, 10.16, 10.52, 10.85]
x =         [ 500,  900,  600,  500,  100,   100,   100,    50]
p1 =  65.95
d1 =   7.07
p2 = 101.66
d2 =   3.80

# calculating
s = s_percent ./ 100
n = length(x)
t = 1:n
a = (1 .+ s) .^ t
df = 1 ./ a
a2 = (1 .+ s) .^ (t .+ 1)
df2 = 1 ./ a2

dfx = df .* x
pv = sum(dfx)
txdf2 = t .* x .* df2
sumtxdf2 = sum(txdf2)
duration = sumtxdf2 / pv

A = [p1 p2; p1 * d1 p2 * d2]
b = [pv, pv * duration]
x1, x2 = A \ b

# output
println("4.13.jl")
@printf("%10s%10s%10s%10s%10s%10s\n", "t", "s", "df", "x", "dfx", "txdf2")
keisen = "-" ^ 60
println(keisen)
for i = 1:n
  @printf("%10i%10.4f%10.4f%10.0f%10.2f%10.2f\n", t[i], s[i], df[i], x[i], dfx[i], txdf2[i])
end
println(keisen)
@printf("%40s%3s%7.2f%10.2f\n", "","PV=", pv, sumtxdf2)
println(keisen)
@printf("%50s%5s%5.2f\n", "", "D=", duration)

println("p1= ", p1)
println("p2= ", p2)
println("d1= ", d1)
println("d2= ", d2)
println("Ax = b")
println("A ", round.(A; digits = 0))
println("b ", round.(b; digits = 0))
println("x1= ", round(x1; digits = 2))
println("x2= ", round(x2; digits = 2))
# eof