build a mine, or invest to astro ?

1/ the simplest mathematical calculation

( mine Production( N+1 ) - mine Production( N )) / cost mine , we call A/B ( everything back in unit deut )
and
How must resource one more planet give you / cost astro , we call C/D ( everything back in unit deut )


To compare we need the denominator is equal


AD/BD and CB/DB
with simplification AD and CB


if AD > CB => build a mine otherwise Astro.


2/ more accurate calculation


when we have a new planet after reseeach 2 lvl of astro, we invest resource to build defense, facilities...
so we could add those resource in addition with cost of astro ( D )

Which mine to build first ?


for each mine :

cost of next lvl mine / ( mine Production( N+1 ) - mine Production( N )) = how much time in hour to profitable

so , build the mine which have the lowest profitable time